Honestly, i've spent well over 1000 hours on the various Gamebryo engine games (Oblivion, FO3, NV, Skyrim, Pirates, etc).
I'm not even sure why. The Gamebryo engine sucks ass, but the games on it manage to be extremely immersive and fun despite all the bugs and graphics.
To that end, i've also downloaded a further 12gb+ of various mods for the various Bethesda games. I have never played through a PC copy of any Gamebryo game without at least 1 mod.
Pokemon, probably upwards of 500hrs throughout them all.