*100+ Hours*
God of War 1,2 & 3.
Morrowind & Oblivion.
LittleBigPlanet.
Resident Evil 4 & 5.
Demon's Souls.
Red Dead: Redemption.
Star Ocean 4.
Dead Space.
Soul Calibur 3 & 4.
Condemned 2: Bloodshot.
Uncharted 1 & 2.
Disgaea 1 & 3.
Cod:MW.
Cross Edge.
Fallout 1 & 3.
Bioshock 2.
Assassin's Creed.
Borderlands.
*Top Contenders (200 And Up)*
Final Fantasy 1 (NES & All Re-introductions/Re-inventions/Updates). ~Uncountable~
Disgaea 2. ~713 Hours, 14 Minutes, 57 Seconds~
Star Ocean 3. ~539 Hours, 12 Minutes, 41 Seconds~
Legaia 2. ~491 Hours, 37 Minutes, 17 Seconds~
Persona 3: FES ~472 Hours, 27 Minutes, 52 Seconds~
Radiata Stories. ~284 Hours, 58 Minutes, 30 Seconds (Most Recent Save)~
Guilty Gear XX. ~Over 200~
Quite Possibly the Ultimate Winner (Definitely over a healthy amount of hours):
Simcity 4 - I would literally play this game for DAYS at a time; nonstop; without turning it off or taking any more than a few hours break a day; for months. MOD packs are... evil...
Wow... I may cry due to my insane lack of any quantifiable Life...
*Late Entry* - The games listed are only in the past year/year and a half. I'm 24 and started on Atari so I'm sure our fellow gamers can agree... Such a question in earnest could fill VOLUMES of logged hours sitting in front of a screen.