Story: Final Fantasy X, Final Fantasy XII, Final Fantasy VII, Final Fantasy VII
Total play time: Starcraft, Diablo II, Super Smash Brothers Brawl (countless hours on all of them)

WoW most likely.

On a console, I think Disgaea and FFX

On a handheld, pokemon over one hundred hours in a couple of those.

Runescape...

I don't want to think of how many hours I put into that game before I ended up quitting.

Zelda TP: 76 hours. I still play it time to time to do fishing, random dungeons, see the aswesome ending again, ride epona more etc.

Though overall super smash bros melee or brawl, but thats obviously multi-player

WoW

warhawk 275hours
FFX 65hours
FFX-2 8hours

longest i played was Zelda: MM i got every heart piece all stray fairies all bottles all masks and biggest bomb and quiver holder.

FFX, FFX-2 or Persona 4 can't really remember.. took around 80 hours each if I'm not mistaken.
If we include MMO's it'd probably be.. Lineage II perhaps? or wow.. takes forever to level in L2

Mass Effect - 52 hours