This is a pretty interesting topic right now, because as more and more people flock to the former counter-culture of gaming, more and more opinions about its genres are flooding in. Frankly, many of those opinions are not opinions at all; they're misinformation. In fact, I'm not even sure anyone knows what an RPG is anymore. Perhaps that's an exaggeration. However, I know what an RPG is.
Things that do not define a roleplaying video game
Yeah, no roleplaying in roleplaying games. I know. But look, true roleplaying is only possible in tabletop RPGs. You don't get it in video games. If you want to call the lite pseudo-morality choices you make in Fallout 3 "roleplaying," well, you're wrong. That's not roleplaying. That's a small group of branching paths -- paths that don't even change the overall direction of the game. It's more like driving in a different lane on the same road -- the path through the game is always identical, even if there's differences in the dialogue or the ending. Ironically, Japanese games like Seiken Densetsu 3 and Radiata Stories have done a better job at making the game actually change based on your decisions, but it's still not like true roleplaying.
The morality systems you see in Bioware and Bethesda games don't come close to approaching the depth available in a tabletop game where you build your own character from scratch. It's not much different from having preset characters in a JRPG -- you just get to choose to be good or evil instead of having one choice. That's what every choice in those games boils down to: it's very black and white, and it's nothing like true roleplaying.
That's not to say games should be criticized for not having roleplaying in them. There's a reason for that. It would be impossible to program that many different possibilities into a single game, at least at this point in time, and even if it were technically feasible, it would take an unprecedented amount of time. So no, there is no roleplaying in video games, and certainly not in RPGs.
Deep storylines/"story-driven gameplay"
A "deep" or "intricate" storyline definitely does not define an RPG simply because it's not exclusive to RPGs. The games with the most mature, complex storylines, in fact, are largely based in the text adventure genre, a genre that is mostly on rails and, largely, has no combat. Grand Theft Auto, as a series, has a more intricate storyline than most RPGs. The same can be said for any number of action and adventure games, even some shooters.
As for RPGs that are "story-driven," can you name a game where progression isn't driven by some kind of story? Actually, you probably can. However, you'd quickly notice that this is also not something exclusive to RPGs. If you're talking about cutscene-heavy games like Xenosaga, all they've done is made the plot intrusive and self-indulgent, while missing the point of why video games are created -- to be played. And again, for every Xenosaga in the RPG genre, you've got a Metal Gear Solid in the action genre that does the exact same thing. Is MGS an RPG? No.
If I had my Johnson drop kicked every time I heard some fuckstick say "I play RPGs for story," I would lack the ability to bear children. If you're really playing RPGs for their stories, you should have stopped after you played through FFVI, FFX, the Suikoden series and Chrono Cross, because those are the only RPGs off the top of my head that approach the pet waste the boot of literary excellence stepped in. How about you play games with good stories for story and stop polluting my genre with your tryhard bullshit? Do you read reviews? Actually read them? That's how you find out which games have stories worth looking into. Better yet, why don't you move to an artistic medium where your faux-hipster ass is welcome? Thanks.
Not to be a dick or anything.
The only reason RPGs used turnbased combat in their infancy was because there was no way to have a more active battle system in a board game. Unless you wanted to look really silly. Or set up a fencing match with your dungeon master every time you encountered a monster. It just wasn't viable, but if it could have been different, it would have.
The turnbased combat model became a part of the standard RPG experience, and naturally, it was kept when RPG video games were first created. No one thought to switch to an active combat system until, if I had to guess, the mid 80's.
Things that define a roleplaying video game
Character progression centered around visible statistics
STR, DEX, AGI, VIT, INT, MND, CHR, WIL, HP, MP, ATK, DEF, SPD, all that stuff. It affects the way your character performs, mostly in battle and sometimes out of battle, as seen in many WRPGs. These statistics, in varying forms, have always been one of the pillars of RPG gameplay. Going with this is the concept of leveling up, whether it's through defeating enemies for experience points or other means, and these statistics increasing for every level gained, whether the progression is set, random or chosen by the player.
Herein lies one of the grand concepts surrounding the RPG: starting out as a fairly weak adventurer and eventually building yourself into a powerful warrior. It's that sense of accomplishment and progress that makes RPGs addictive, fun and definitely not for everybody. It's the genre most demanding of your patience to truly enjoy, but it can also be the most rewarding if you're willing to take the time for it. This sense of gratification is only enhanced in MMORPGs, due to the fact that everyone else can see your progress for themselves, and the sense of companionship you build playing with other people.
I would argue that those of us who think a compelling plot is the most important thing in an RPG are really just looking for instant gratification, because they don't actually have the patience for RPG gameplay on its own. Then they cover it up with "LOL u dont play rpgs 4 gameplay, if i wanted 2 have fun i wud go play halo." You know, fake ass motherfuckers.
Random number generator/dice roll
The random number generator, or dice roll if you're playing a board game, is a vital element of any RPG. It helps to decide a ton of stuff, including but not limited to: damage dealt and received, encounter rate (when applicable) and item drop rate.
In determining damage, the RNG produces the element of "randomness" (though it's not truly random, we'll just call it that because it fits - look it up if you're curious) that you see in RPGs. You notice how your attacks don't always do the same damage -- that's because every attack you launch goes through a mathematical formula that includes your attack power, the enemy's defense, any special modifiers for your attack, and a random variable which is produced by the RNG. This creates a damage range for your attack to fall into.
It's the same thing for encounter rates: every step your character takes has a chance of entering you into a battle. In some games, the chance will increase with every step, while in others it's set in stone, but the timing of the battle itself is always determined by an RNG. Drop rates are the same. So are many things -- the RNG is so deeply ingrained into the gameplay of an RPG that I'm not sure you could make one without incorporating it in some way. Without it, you get Zelda, which is something many people confuse for an RPG, but it really isn't. Then again, it's used in virtually every other genre as well, including sports games. However, RPG is the one genre that uses it as a central element, with almost everything that happens during gameplay being affected by it in some way.
What, you thought there would be more? No, that's all. That's all that defines the core mechanics of an RPG, western or eastern. It's funny, because everyone thinks it's so complicated. It's not.
Oh, you want to talk about WRPGs and JRPGs? Why? That is a dead ho-
You know what, fine.
What's closer to a "true" RPG: WRPG or JRPG? Which has better storytelling, etc.?
WRPGs, or "western roleplaying games," have sat squarely at opposite ends of the RPG spectrum from JRPGs, or "Japanese roleplaying games," since the late 80's. What really separates them?
Truth be told, not as much as you think. As discussed above, WRPGs tend to give you the illusion of many different paths to take when there's usually only two, or maybe three, with the structure of the plot remaining mostly the same regardless. JRPGs don't bullshit you -- you know right off the bat that the ending is going to be the same no matter what you do, aside from arbitrary or pointless stuff that adds extra scenes to the ending, or changes it slightly, or whatever.
As far as gameplay goes, WRPGs tend to have you build a custom character with a class and stats of your choosing, then send you on a fairly non-linear quest in a horribly generic Tolkien-esque fantasy world. Other classic western franchises are sometimes ripped off too, like doing sci-fi stuff in a Star Trek-influenced universe, or actually playing within the Star Wars universe in Knights of The Old Republic. The combat is usually realtime, or "pseudo-realtime" as seen in many Bioware games, and generally has very little depth or strategy involved.
A common feature of WRPGs is the ability to perform various actions outside of battle that are influenced by your stats, such as lockpicking (DEX), computer hacking (INT) and persuading NPCs through dialogue trees (CHR).
As for storylines, you get boring, standard fantasy that seems to have been written by people who are still fascinated by dragons and stuff. You know, 12 year old shit. As a whole, storytelling in WRPGs is uninspired and dry. The Fallout series (1 and 2, mostly) is an exception to this, boasting some of the better storytelling in gaming, though it is set in a decidedly Mad Max-influenced post-apocalyptic United States. Mass Effect is another example of solid storytelling in a WRPG.
In JRPGs, you have preset characters, though many games put an emphasis on equipment and skill customization. You replace generic Tolkien world with generic animanga fantasy world. Gameplay usually has a heavy focus on high-rate random encounters, turnbased combat on a separate battle screen and flashy special attacks. JRPGs as a whole are much more linear than WRPGs, but with that, you tend to get a tighter, more polished game world.
Storywise, JRPGs are conflicting, because they generally try very hard to be complex and to appear mature, but perhaps because of the translation to English (but probably not), this effort can never seem to escape being ultimately trite and overwrought. The one-dimensional, annoying, inhuman and archetypal characters don't do any help to back it up, either. What you get is a big, sloppy mess of bad writing and a half-baked plot that's far too unbelievable to ever relate to. Any moralistic or political allegory is lost in this. Some may call it a cultural difference, I still call it awful storytelling.
They just informed him that he's going to grow up to be the lead singer in an Evangelion tribute band
Basically, they're the opposite of WRPGs -- instead of being uninspired and dry, they tend to have too many ideas and not enough talented writers to make something great out of the good ones while throwing out the bad ones.
WRPGs and JRPGs are the same under the hood. Their battle systems, storytelling, art style and pace all tend to differ, but they borrow from each other often and use the same mechanics to build their gameplay over. If I had to say which is "closer" to the "true" RPG, it's definitely the western style. I'd say that Japanese RPGs tend to have more interesting plots, if we're disregarding all the crap that gets shoveled into both sides. That's just an opinion, though.
Still, I really don't think JRPGs and WRPGs are different enough that they should be considered separate genres from each other. Different schools of the same style, sure, but not completely divided. It's a common sentiment among foolish people that JRPGs are somehow "not really RPGs." This is not true.
Sadly, most gamers are not adept at analyzing their own arguments. Or anything, really. This is the double-edged part of free speech and encouraging the exchange of ideas: misinformation is spread, and there's not a whole lot you can do to stop it. Already we have a whole generation of people who think Xenogears is good and Final Fantasy XII is bad, and it's only going farther down from there. We have people saying that Bayonneta "rips off God of War." That is beyond sad.