The main thing that gets me hooked on a game is the storyline. What are some of the best? Preferably on PC and with modern graphics (ie, no Fallout 1/2, or Planescape Torment, even though the stories were great).
For me:
Neverwinter Nights with all the expansion packs.
Call of Duty (the stories were great but disappointingly short).
Dragon Age
The Witcher 1 + 2
Dear Esther
Amnesia the Dark Descent
Mass Effect 1+2+3
Skyrim (short main story, but a crap ton of other side quests made it up)
Fallout 3
Metro 2033