Which game do you have the most play time on and why do you think you enjoyed it so much?
Mine would have to be Old School Runescape (or Runescape back then).
Everyone at school would hang out in the playground and talk about it every day, then I'd come home from school and play it every day. It was such a new gaming experience. You could travel around a large world, see other players actually play in game.. the progression feeling you got upgrading your stats for the first time..man it felt like home :P