15-20h!

10-12 hours is fine for a single player game as long as there is some replay value (branching paths, open world with lots of side quests etc.).

Otherwise, 16-20 hours is about right for a single playthrough only sort of game.

I'm not buying games @ 60 bucks period, no matter the content.

at least 40 hours

It should be 20hrs+, I'm fine with 3€/h, that's comparable to visiting the cinema.

30. 2 bucks an hour.

Always depends on the game

8 hours with 110% Action/Story/Entertainment like in God of War/Uncharted and stuff or 15 hours complete boredom?
I take the 8 hours and support great developers.

It depends if it's an intense linear game like Uncharted or God of War (then 10-12 hours are ok if the game's good) or if it's less intense but larger like Far Cry, Saints Row or Borderlands (20+ is a must). In fact, Borderlands 2 was too long for me to do all the side missions.

Well it depends on the quality of the game. Which is why I always buy God of War games within their first week, becuz even though they are short, they give me an unparalleled out-of-this-world experience. Which is why I am even more excited for Ascension next year, becuz it has amazing multiplayer (I saw it on IGN).
But if the experience is short AND low-quality, then its definitely not worth my bucks.

I only pay full price for like 2 games a year. the rest i buy on sale.