Let's face it: We can't stop playing certain games.  Whether it's addictive combat, tons of replay value invested in second or third playthroughs, or just a huge appreciation for the game in question, we all have those games that we've logged countless hours into the single player alone. 
 
It's easy to play eighty million StarCraft matches or spend several nights on Halo: Reach binges, but there's something to be said about reaching triple digits on single player.  It means that without online match lobbies or extensive replay to be found in online tournaments, something drove us to put over 100 hours into a single-player story.  Hell, maybe you just spent 90 hours obsessively hunting for achievements.  Either way, it's a huge accomplishment that signifies what a game means to you.

So here is my venerable list of these triple digit titles.  Maybe at some point down the line I'll make a multiplayer, although that still feels a lot easier. 
 
Tales of Vesperia - This is easily one of the best RPGs I've played in a long time.  The story will run you a very respectable 40-50 hours, but with New Game+ there are a lot of great reasons to replay it.  At the end of the game you can spend a form of currency, GRADE, to acquire New Game+ upgrades like 2X normal experience, 10X normal experience, unlocking additional content, or even unlocking a new difficulty level.  After logging 60 hours into New Game+, I broke the 100-hour mark and actually got an achievement called "Too Much Free Time".  I'm not arguing!