Dragon Age: Origins. (Dragon Age 2 is decent, but not as good)
The Elder Scrolls: Morrowind, Oblivion and Skyrim (ordered from oldest to newest).
Torchlight 1 & 2
Diablo 3 (don't expect it to be as magical as you may have remembered Diablo 2, and it'll be good game).
Titan Quest: Immortal thrones
The best part of the trilogy is the overall story and dialog options. Some choices have consequences in later games. Mass Effect 2 is probably the best of the three because of the various DLCs that expanded the game a bit. Mass Effect 3 has only thus far released only 1 DLC which has added additional gameplay. The 1st DLC was really just the expanded ending which offered a bit more closure than the original ending, but does not change how the trilogy ends.