Warcraft III probably. The only game that me and my friends had in common, so we'd always play Wintermaul together. Wintermauls were a blast, until everyone started blaming grey for everything.
If you have played Wintermaul, you know what I mean.
Although I've actually put quite a few hours into my FFXIII file, approaching 65. Lost Odyssey I have like 67, but I've done nearly everything in that game, while I'm only done half of the Cie'th stones in FFXIII...