The thing I like about RPG's (some of them) is the customization - being able to alter my characters to cater to the style that I want to play. But what ruins most RPG's for me is that, they're like Strategy games - only without the strategy.
I could write a long rant about what I hate about RPG's, and dammit, I'm going to.
Try playing KOTOR, or WoW, and then play Starcraft in a custom "RPG" map where you play as only one character. They really play the same to me in terms of combat. Sure, they're fun for the first five minutes, but then the novelty of leveling up and choosing your character wears out when you realize how limited the combat is. The people who cry out "NOOB" when someone dies are absolute retards, because calling someone a "NOOB" implies that they have no skill, when the damn game doesn't require skill at all.
Take two players in Diablo 2. Have them both play as Paladins with the same level, skills, equipment, etc. Have them fight each other several times, with different players taking control over the Paladins after every fight. Notice how the result is almost the exact same every time, one Paladin wins over the other simply because the little percentages in the Paladin's stats just happened to work in the player's favour.
Now have several groups of two players in Street Fighter 2 playing each other, with all of the players playing as Ryu. The results will be vastly different, because of the players' skills, not because one of the Ryu's happened to magically misfire a Hadouken.
How you can improve upon RPG's is...
Get rid of random chances (stats) - The thing I hate most about RPG's is that when I die, it's not because I made some really stupid mistake, I didn't react quickly enough to an enemy's pointy stick heading in my direction, or I just suck in general - It's because my CHARACTER sucks.
Get rid of random chances (items) - So I played Diablo 2 once and I found this sweet sword in this one place. My character ended up getting deleted somehow, so I made a new one. I go to the same place, kill the same enemies. No Sword. Bullshit.
Get rid of grinding - KOTOR got this right. No respawning enemies, and you reach the level cap by the end of the game. Alternatively, you could fix the problem by having a low level cap that increases as you progress through the game (ie, no getting past level 5 until you've beaten the first boss)
Get rid of random encounters (see Paper Mario) - Random encounters are especially annoying if you're in a dungeon, trying to solve a puzzle, and then all of a sudden, without ANY WARNING WHATSOEVER you have to fight. Then after you're done fighting, you have to try to remember what the hell it was you had to do, or were trying to do before said encounter.
More balance - it seems that a lot of RPG's have a habit of allowing you to combine certain characters/skills/boosts to become godlike. For example, in KOTOR, level up Mission's ability to use a repeating blaster, along with her sneak attack ability (ability to use a gun that hits a lot + ability to do a lot of damage per hit = OWNAGE CANNON), and you'll be bloody unstoppable.
Some people will say that that's strategy. Really, that's not any more of a strategy than massing Carriers in Starcraft. Any shmuck could go to Gamefaqs and look up "insert cookie cutter build here".
And Diablo 2 is full of assholes who, if you have the audacity to play as a Paladin who doesn't use Blessed Hammer, Zeal/Fanaticism, Vengeance/Conviction, etc. will fill your screen with cries of "OMG NOOB U SCK BALLZ." Seriously, one of my conversations went like this
Some Guy: Dude, why are you using a Pally with Charge and Holy Freeze (as opposed to insert cookie cutter build here)?
Me: It's more fun
SG: Okay then, have "fun."
Needless to say, my faith in humanity was shaken that day.
Have the player actually have some control over their characters, besides telling them to "attack (insert enemy here)" or "use (insert item here)". (once again, see Paper Mario). The whole "doing stuff only by moving the analog stick through the menu and pressing A" thing is dull, mainly because it's slow. Megaman X Command Mission had an interesting way of alleviating this. Each attack was assigned to a different button, so instead of selecting "Missile, Missile, Charge Shot" through a menu, you just pressed "X,Y,R." There were also a few action commands ala Paper Mario.