RPG is a hard genre to nail down. I keep my wants rather simple, I think RPGs are games where the player has more to add to the game than mere skill, there are rewards for playing the game that drive gameplay and part of the fun is planning the Rewards. It's a very broad Genre and while often story matters, a lot of times it doesn't: The Diablo and Might and Magic series are very storyline light but excellent RPGs in their own right for what they do.

That sounds horrifying. O_o

But I agree with you, this is the core for me:

Uh, no. CHOICE means in-game choice both story-wise (that is, divergent story paths depending on character) and gameplay-wise (different ways of handling situations, unique opportunities for different characters). Or, to put it another way: A roleplaying game is a game that allows for a significant amount of roleplaying. :)

Some games pull you in and make you feel like you part of an experience. Some don't. Make me feel like I'm there and doing something that matters. That's really all I care about. Oh and make it enjoyable.

Many different things make a great rpg. One of the most important in my experience is fun leveling up like in Morrowind, Baldur's Gate (and it's like), Fallout, etc. I like having to understand the leveling system so I have to plan ahead, have the right attributes, class, skills. Even more important is the world, it should have an epic scope to it, it should feel like a living breathing world(s), there should be unique characters and many different things to do that have nothing to do with the main quest line. I like a wide variety of weapons/armor, as well as the ability to craft things like alchemy and weapons. Most important perhaps, is the combat if it's not fun and exciting then the game will start getting boring sooner rather then later. Having many different options to how you can fight helps keep things interesting, whether you use magic, stealth, or blade, and the weapons/spells you use will alter how you fight as well, variety and choices is key. Finally, a great rpg leaves one with a feeling of achievement after you advance to the higher levels, as well as seeing an effect on the game-world based on what you do. Anyways, this is some of what makes a great rpg in my opinion.

Hmm, for me, that's a hard one to call.. but I have a few:

1) must be remotely forgiving at the beginning- I'm not talking 'no permadeath' or anything, but when an RPG just randomly throws you in to the deep end with no way to even know what you can/can't take on, and you die repeatedly 5 minutes in to the game? That makes me put the game away and never come back.

2) There has to be a story hook /early/ in the game, and the story must actually draw me in- Morrowind is a classic example of a game that might have otherwise been good, but never managed to hook me in to the story.. as is Planescape.

3) Levelscaling, to an extent is fine, certain types of foes getting tougher as you do, but not staying at your same level can be good. - Exception, in action RPGs ('Diablo Clones') I like level scaling)

4) When there is no form of level scaling, the game shouldn't inundate you with side quests- If you do them, you out level the content for a while. If you don't do them, you're probably going to be too weak.

5) When there is any form of level scaling.. side quests should really be optional. - If you want to follow the main story, you shouldn't feel you have to stop and grind before you can continue.

6) Side quests should make you want to do them for reasons beyond "It's extra loot!".

7) If it's a party game.. you either need to control your other characters or fine-tune their AI.

As you can see, I have a lot of elements I really want in an RPG, which is why few are great, to me.

I also prefer isometric, turnbased RPGs.

I don't think their linearity is that much of a problem. It cuts back a bit on replay value, but sometimes freedom can be sacrificed in order to get a tightly woven story.
My issue with JRPGs is that they tend to get very repetitive, trying to fit 15-20h worth of story & gameplay into a 50h game. And angsty teens. Most of them seem to contain angsty teens (or at least people who behave like angsty teens).

This.

As there is no clear cut definition of RPG, there can't be a clear cut definition of great RPGs.

I consider ME 2 a great RPG for its excellent immersion, characterisation and choice & consequences. Other say it is not an RPG because it doesn't have enough numbers.

Not a question of numbers. I didn't feel choices and consequences because pseudo-RPGs like ME2 are just a series of missions/levels/corridors-to-clean-up that you can do in a certain amount of different orders. Most of the game is being stuck on a "world", playing some linear third person doom3, killing all the monsters, and going back to the ship to select the next "game world" to "complete". In that sense, it's as much a RPG as Jedi Academy, or any other action game where you have to manually select your next assignment.

And it's got some numbers throwed in. And that's actually what game it a fake rpg-ish flavor. Customisation. But in general, I find very non-RPGish the games that lock you in one mission, after having locked you in another mission, before locking you in another missions. They are just arcade games with, at best, branching "levels". Stats or loots matter much less than the game structure.

So, back to OP, maybe a major criterion for me is a seamless world, like roughly one big level (with loading zones, for caves, towns, etc), where you can go back and forth freely, not feeling you interrupt a sibgame or start a subgame each time you step out or in of somewhere.

Even arena-locked bossfights break the rpg-ish impression to me. So, with that in mind, you can imagine that not only I'm reluctant to really see Mass Effect as a real rpg, but i just scream when people call Alpha Protocol one. Yet the branching system of Alpha Protocol is said to be much deeper. But it's still just about mission selections.

Choice-consequence is one the most important aspects for me.

Epic title, for starters.

"Dragon Age" is quite epic, because it has both "Dragon" and "Age" in the title, both of which are quite epic words in themselves. The title just oozes of epicness (or is it called "epicity"?).

But if you take something like "Dink Smallwood", it instantly fails to be epic. I don't think there is a single person on earth or outer space who thinks Dink Smallwood is more epic than Dragon Age.

I'd like to think that player skill should matter in an RPG. I'm not talking about eye-hand coordination and stuff like that but rather having the skill or knowledge or ability to analyze a situation and then use the character's abilities in a way to get the best outcome.

Of course on could always grind five more hours and then come back and simply brute force one's way through the situation, but I guess I don't like grinding. It bores me.

In many replies people seem to say that game ingredients that they like are the very ingredients that make a RPG a (real) RPG. Be it story, immersion, making of meaningful decisions etc.

I don't understand your insistence to call games you happen to like the most "RPGs", even if they aren't necessarily that. You could simply say that you happen to like games that e.g. immerse you completely to the gameworld, or let you make meaningful decisions that affect the gameworld. Even if they are "mere" action games, strategy games, simulators, whatever. Or even actual RPGs.

Per my definition of RPGs, I know lots of both poor and great RPGs. I don't say "I happen to like these games the most, so I'll call them all (real) RPGs."

For example, I usually prefer RPGs that have turn-based tactical combat, instead of e.g. action-based combat. But I don't feel tactical combat is the essence of RPGs, in fact it has nothing to do with the game being a RPG. I just happen to prefer party-based RPGs that have combat like that.

I'm actually against this, since I have often abused it in Pen and Paper rpgs. If I can solve the logic based riddle in 1 minute, why does that mean my Half-Orc Barbarian with 6 intelligence should be able to solve it in the same amount of time? Just like you don't expect a weight lifter who plays a fragile (but highly intelligent) mage to be able to lift ingame 200 pounds, it is (imho) cheating to expect an intelligent player controlling a stupid character to be able to use the player's intellect in place of the characters. PS:T did have that, by forcing you to use the character's intellect for the logic riddles, not the player's.

On Topic. For me an great game is one that pulls you in, and gives you the "Oh crap, it's 4 o'clock again, why am I still playing?" feeling. There isn't a specific set of things that I can quantify, a game either has it or doesn't.