Depends on the game. I'd rather action, shooters, etc. stick to a 8-12 length. Really, length doesn't matter as much as quality does.

Heavenly Sword is better than more half of the action games this generation and its only 5 hours.

That said, RPGs longer than 40 hours are too long.

 Now that I think about it.. I bet the next Halo would cost $400. O.o

It really depends on the game. I don't want arcade type games lasting too long, but I don't want RPG games being too short.

I can't even give you an estimate, because there are way too many things that go into it for me to lay out nice and easily.

dont give microsft any ideas.

I say 15-20 hours is the sweet spot for most. Games that wanna be epic like Zelda or RPG like 30-50.

Anything past 50 hours is overkill.

Ive been playing Siren:Blood curse for over a month and i still havnt finished it !! the funny thing is each chapter is about 10 minutes !

I'm more or less on CGI-Quality's page.

Although I do take into consideration the "what am I spending here per hour or how much am I willing to spend per hour"-rule.

15 or less is terrible. I won't buy a game like that.

20-30 is decent, it won't add a lot or take a lot away.

40-50 is good. It definitely makes me want to buy the game, even if it isn't that good.

60 + is fantastic.

Perfectly, I'd like it to be 60 hours storyline, 140 hours of side-quests.

That's the perfect. For a strategy game, it would be even more - 400 +.

Platformer would be more ala 150 hours main game.

To say it simply - a game CANNOT be too long.

40-60

15 hours maximum for me. Anything more and I get bored. If I like a multi-player, however, I can go on playing forever.