What's the perfect length of any given game?

[twesterm]

It use to be only the 60+ hour games for me, now I much prefer the 8-12 range. If the game is more than that, I'm just likely not to finish it.

On top of that, I also love games like Mario Kart, Excite Truck, and House of the Dead: Overkill that I can play and just have fun for 15-20 minutes.