lufia 2 i played it for aout three months straight (i know ur thinking i have no life but i rarely do this so back off) i got up to the second to last boss in the game just to have it all erased in front of my eyes! i was inches away from snapping the game in half (if u snap my game ill snap ur neck)
Been on a City of Heroes kick lately. It's addictive. Otherwise, I remember playing Crono Trigger. A lot. I managed all the endings and still kept playing.
I would say Darksiders (PC). Don't know why but I have finished this game twice (the second time i got every shard, bonus, item, etc.). Just LOVE this game.
I think the most addictive game I have played is probably Sid Meier's Civilization V. I played 4 right before 5 game out but i didn't like it because the graphics stunk and it was all square. yup. Fun game if any of you guys like turn based strategy games.
Team Fortress 2 is the single most addictive game ive played, i have 380 hours of gameplay on it in less than a year. Its constantly updated with new weapons and never gets old.
Most addictive game I have ever played would have to be Gran Tourismo 3. Spent weeks unlocking all the cars/tracks/tournaments. I still go back to it from time to time for a couple races.