A few corrections I'd like to make. Only Campaign, of course, as the rest is too variable.

God of War - Average: 9 hours

God of War II - Average: 11 hours

Shadow of the Colossus  - Average: 12 hours (maybe I'm just slow lol)

Assassin's Creed - Average: 11 hours

Resistance 2 - 7 hours

God of War: Chains of Olympus - 7 hours

And some others:

Metal Gear Solid 4: With every cutscene: 25 hours, with no cutscenes, 15 hours.

BioShock: 12 hours (or so)

Tools of Destruction: 10 hours

Most games are around 10-12 hours, for me.

MGS4 has 7 hours of cutscene?

Talk about boring(I hate cutscenes if they're over done)

Dragon quest 8: about 80 hours to complete. theres a few things you can do after completeing the story which can move that time up.

Okami: about 40 hours average. depends on how many side quests you do, could add about 20 hours to that if you are a completist.

Minimum. Probably more, around 8-10 hours. They get repetitive sometimes, but the more awesome cutscenes completely make up for it (beginning, end of Act 3, Big Mama, ending)

Found some more saves:

Shadow Hearts Covenant: 73 hours
Shadow Hearts: From a New World: 55 hours
Kingdom Hearts: 64 hours
Kingdom Hearts 2: 70 hours
Dragon Quest 8: 75 hours
FF VII Crisis Core: 80 hours
LocoRoco: 40 Hours
Patapon: 35 hours
Metroid Prime 3: 15 hours
Metroid Prime 2: 12 hours
SMG: 23 Hours
Super Smash Bros Melee: 65 Hours
Shadow Of Colossus: 17 Hours

@ lestatdark

At least you get your moneys worth...
You got to the tower in PE i saw, somehow i couldn't get there, must have missed something but can't remember what.

FFX 110 h
Shadow Hearts : 60 h
FF VII : 120 h
FFVIII: 90 h

@weaveworld

The chrysler building in PE is only available during the second playthrough in the game, it's unlocked in the Second Day, when you have access to the NY map. But I only recommend you going there after you defeat the T-Rex on the museum at the Fifth Day, since the enemies there are hellishly strong, and the bosses are stronger than the final boss of the game. Also, the final boss at the top of the Tower was trully a shocker xD

I think the GoW PSP one might be a bit high, I beat the game in about 3-4 hours. It was my first GoW game and my first PSP game.

I beat MGS 4 in 14 hours watching all cutscenes. So actual gameplay is about 8-10 hours + cutscenes 4-6 hours.

Hmm. Might give it a shot someday soon. Thanks.