The jRPG's in my life, mostly.
1) Finalf Fantasy IX: somewhere between 450 and 550 hours, I figure... Playing it out multiple times and ever since my second playthrough, getting 100% within the game (apart from Excalibur II, having to play a game out in 12 hour simply takes the fun out of it). Every now and then (but not more than once a year) a go for another playthrough. Ah, nostalgia...
2) Shin Megami Tensei: Lucifer's Call: almost 300 hours I think... Trying to nab all 6 the endings you know. Two down, four to go. Luckily, the worst one (true demon ending) was the first one I did. Christ! The clock stood at 160 hours when I finally beat Lucifer's butt, had to do a lot of preperation there...
3) Probably one of the platformers I've played so vigorously over and over again: Either Crash Bandicoot II: Cortex Strikes Back, Spyro 2: Getaway From Glimmer, Ratchet & Clank 2 or Jak II: Renegade. Huh... Look at al the number 2's...