My game with the most hours in it is probably like, Dota 2, back when I was in college and still had lots of spare time with my friends. A game like that is a huge time sink to be good at though, and I always lagged behind my friends. So it's for the best I don't play that anymore.
For my addictive games were three: elder scrolls three morrowind, jade empire and star wars kotor. I played all three games on the original xbox. I first played and beat star wars kotor then went to the local game store and baught the other two. I got elder scrolls morrowind goty edition, couldn't beat the game because of the glitch, but I still got bad grades in school from staying up till two in the morning playing these games.