Since some of my other favorite answers have been taken up I am doing darkhorse candidate.
YOU clowns are on drugs! DRUGS! YOU people are high!
You can hardly deny that it's an excellent game. It is not, however, suitable for everyone. Theres' just too much text for me. While I certainly like a good and expansive story, playing for 5 hours straight without sticking my blade into a single enemy was just too much for me, so I quit about halfway through the game.
As for myself, my favorite PC style RPG's are, in no particular order: Dragon Age: Origins, Baldurs' Gate II and Neverwinter Nights (at least if you're allowed to count the fanmade content. The original three modules from Bioware were good, but certainly not groundbreaking). I would also like to say Mass Effect III with expanded ending, but in my opinion it's more a shooter-with-story with RPG-esque upgrades than a fullblown RPG.
fallout 1 ,2 and botherhood of steel baldur gate planetscape torment icewind dale dragon age: origins the ultima series, 6 7 and 8 are the best for me at least might and magic series (not the 9 though....) mount and blade rage of mages elder scrolls 2 and 3
these are what I remember though and not considerating the MMO around