Considering that I've played both Diablo 2 and The Witcher, I could easily say it was the best RPG I've played till now!
from the very first moment you start creating your character you realize this isn't just an RPG; there are six different ways you can begin your game(if i'm not mistaken) depends on the kind of race and class you choose. when you set your foots in the game the very fist moment the beautiful graphics, character animations and perfect lightnings charm you enough to go and finish the game! but this isn't just it. this game has one of the strongest beginnings i've ever seen and although you don't know the characters at first but you start to care about them! the game's lore is very rich and the story is absolutly amazing and it sucks you in like no other RPG could!. the combat system is very tactical and very deep thanks to the huge number of spells and abilities although sometimes it might get a little bit hard and frustrating but with pausing the game and a little bit thinking you are gonna overcome that little problem. the enviroments are brilliant and although the game is open-world and big but you won't get lost in a huge area with lots of objects, loots and so many paths to go around(like Fallout and Oblivion) and that is one of the things that i love about this game. the sound effects are magnificent and hearing the sound of your armor and footsteps while walking is really fun and sound of swords and melee weapons are extremely realistic.
But now lets go to the two little problems that i had with this game: the first and the most important was rewards and loots; they weren't satisfying and surprising at all, and the other one was the musics; you know, some of them were cool but generally i expected an epic and touching music like the ones in World of Warcraft and Diablo but sometimes it was really good.
So, this was an amazing and mind blowing Role-playing game that every RPG fan must play it and i personally believe Dragon Age: Origins is the best RPG till now and the best game in 2009 and it really deserves to be the Game Of The Year.