I've spent by far the most time on the Infinity blade games, but other than that, Bad piggies Shadowgun Deadzone NOVA 3 multiplayer MC3 multiplayer GOF 2 HD (galaxy on fire) Real Racing 2 HD
I'm ashamed to admit... It's amazing how much time I've put into some of the games I have... Let's see: Hunters 2, by Rodea Games. I've put at LEAST 150-200 hours into that... It's always on my device, no matter what. Modern Combat 3. No longer on my device, because I've literally played it to death. I've done the campaign in all 4 modes, at least 3-5 times a piece. That's like, 12-20 campaign play-throughs. Reckless Racing 2: Put alot of time into this one as well. Minecraft PE!!! Bike Baron. I love creating my own levels. As complex as I can make em'. Fieldrunners 2 - never gets old. Always something to do on there. Just downloaded Bastion now that it's universal, and I got an iPod Touch 5G. I can already tell this is the best game ever. There are a lot more games I love, but none have sucked up as much time as these. PS: As a bonus, when I was jailbroken on my iPod Touch 4G, I played bloody-hundreds upon hundreds of hours of Pokemon Ruby, and Fire Red. Can't wait till I can get my ROMs on my iPod Touch 5. Untethered Jailbreak soon please!
Tiny Tower, Death Rally, Galaxy on Fire II, Jubeat (JP game, jukebeat in the US store), Chaos Rings (original)