Unless the game has a timer then I have no idea how many cumulative hours I've put in a game, but I'll ist a few games.
Final Fantasy. I've played the NES game atleast 20 times over, Origins twice, Dawn of Souls atleast 10 times, and Anniversary once. It's 5-8 hours, another five hours for the optional Dawn of Souls/Anniversary stuff, so just taking an average of eight hours per playthrough, 264 hours atleast.
Castlevania. I've finished this one hundreds of times. I'd say easily over 100 hours on a game that's only 15-20 minutes long.
Brigandine Legend of Forsena. Another 200+ hours.
Then there's fighting games. I just recently started Dead or Alive 5 and in player data it shows 10 hours. Going by that, I'd say somewhere between 200-500 hours on some fighters.
The highest times I have on some of my saved data. Jump Ultimate Stars shows 99:59:59, Yakuza 3 shows 88 hours, Dragon Warrior 7 was somewhere within 70 hours, and Tactics Ogre was somewhere at 80 hours my first save file.