In no order, because it would take me an hour to get that.
BG2, NWN2, Warcraft 3, MotB(NWN2),

Anyways, why is W3 on the list? Because more than any other game, any other it keeps bringing me back. I have played Warcraft more times than BG2. And probably 3 times since I last played BG2 some 2-3 years ago. I'm not fully sure what it is that keeps bringing me back, the story is good, and the units are fun, but I wouldn't suspect that much. Oh well.
And MotB gets on the list for taking me to Act 2 with a character I decided about 2 hours before that I didn't like. NWN2, well they give you some good and compelling things at the beginning, with some very fun interaction between your party and with it. (Though I commonly forget to talk to them). And BG2, well they have been the game which I compare so many others to, for story and interaction, even if I do not play it as much anymore. And even after all this time, I can still write fanfic for it, something I haven't commonly done for almost any game.