100 hours isn't that much. I bought the C&C First Decade last Thursday and Xfire says I've played 19 hours of Generals: Zero Hour alone since then.
Having said that, I only clocked just over 100 hours on Fallout 3, with my second (Platinum trophy) save taking around 61 of those.
Most played? No idea honestly, but to throw some numbers out there I've probably spent over 800 hours across the PES series, at least 250 across FFX and FFXII (XIII on preorder atm), and 45+ hours on Borderlands (which would be more but my PS3 is currently broken).
I kind of wish that PS3 recorded time played for each game. I downloaded Xfire 2 weeks ago purely because someone told me it did that (after I complained that Steam only does it for games run through Steam).