The "favorites" Megamind, and Terminator Salvation. Both can be beaten in under 5 hours. Megamind Just play through the game. NOTHING'S Missable in there. For Terminator Just play the whole game on hard. Easy!
If you're into RPGs, Last Rebellion comes close. It's probably closer to 15 hours (give or take) if you know what you're doing, but shouldn't be any longer than that.... and far shorter if you use a guide to walk you through everything.
I've noticed a lot of easy s mentioned on crappy games. How about good games? I saw a few there but, for the most part, they are crappy.
Rocketbirds and Trine 2 are two of the easiest s ever. You can probably get the on both games for less than eight hours total. Trine 2 because you can get the in like 3 hours of game play (even before you finnish the game). However, both are excellent games that are well worth their price.