For me it is a
The Lost Crown, but in this forum everyone knows how good this game is
So I choose
Gothic 3 (i can see the point why it isnt so popular, but I think its a so far best RPG in five years period). Next would be
Far Cry 2, which I played recently and as a third Gothic, this game is quite awesome in non-linear gameplay.
I also enjoy
GTR2,
Eschalon: Book I or new
King's Bounty.