Portal 2 - 6 hrs

Killzone 3 - 5 hrs (normal diff)

Dead Space 2 - 7 hrs

Spyro 3: Year of the Dragon (PS1) - 10 hours

Ape Escape (PS1) - 9 hours

Great thread! Why didn't I find it until now?!

Anyway, my personal times:
(I put a * in front of the games that I have pretty much similar hours to the main list to save your time Gilg, so u can skip those)

Assassin's Creed: ~18 hours
Assassin's Creed II: 31 hours (with both DLC. Without DLC ~27 hours)    - What the heck with Assassin's Creed how people rush through them!
*Bioshock: ~15 hours
Dragon Age: Origins: 76 hours (with all DLC but not including Awakening. DLC took around 10 hours)
*Dead Space: 15 hours
Risen: 40 hours
Dark Messiah of Might and Magic: ~15 hours
Dante's Inferno: 13 hours
God of War 3: 17 hours
*Alan Wake: 11 hours
Red Dead Redemption: ~40 hours
Fallout 3: 65 hours
*COD Modern Warfare 2: 6 hours
*Uncharted: 12 hours
Wolfenstein: 11 hours
Demon's Souls: 68 hours
Mount & Blade: Warband: this is hard to measure because the damn game never seems to end but I've spent at least 80 hours and I've conquered about half the map.

*Oblivion: those 130 hours on the official list sounds reasonable (glad you guys took your time) although I personally spent at least 3-400 hours on my first playthrough but then I'm a fanatic about this game.

Crysis - 8 hours on Hard (how someone can take 12 hours to finish it is beyond me o.O).

Silent Hill 2 (PS2) - 8 hours

I just noticed that the games begining with 'Si' are not in alphabetical order. They should come after Shing Force instead of being before Shadow Complex

Top of my Head, includes taking the time to collect stuff and play out the game.

Oblivion - 125 hours

Morrowind - 200 hours

FFXIII - 80 hours

Folklore - 25 Hours

Crysis Warhead - 5 hours
Crysis 2 - 9 hours
Portal 2 (SP mode) - 6 hours

Metal Gear Solid 2: Sons of Liberty ( PS2 ) ~ ( 12:32:41 )
Metal Gear Solid 3: Snake Eater ( PS2 ) ~ ( 15:55:03 )
Uncharted: Drake's Fortune ( PS3 ) ~ ( 8:40:00 )
Heavy Rain ( PS3 ) ~ ( 7:00:00 )
Final Fantasy XIII ( PS3 ) ~ ( 38:38:04 )
Dead Rising 2 ( PS3 ) ~ ( 20:00:00 )
Uncharted 2: Among Thieves ( PS3 ) ~ ( 10:24:00 )
Batman: Arkham Asylum ( PS3 ) ~ ( 10:50:00 )
Metal Gear Solid 4: Guns of the Patriots ( PS3 ) ~ ( 16:14:25 )
L.A. Noire ( PS3 ) ~ ( 18:23:00 )

Whoah! You take your sweet time playing JRPG's. I beat Lost Odyssey with the DLC and got every achievement in about 60 Hours. How is it possible to have played longer? It is linear. Same with Enchanted Arms, FFVII and FFX. The rest I didn't play/beat.

Gran Turismo 5 - minimum 8 hours.

To get this short time, you only have to get to the ending credits, and it counts as a game beat correct? You don't need gold in all events, or max out your level right? To get to the ending credits, you have to play until you are level 14 and then beat the Championship Cup in Professional Series. You can do that easily by buying a 2007 Nissan GT-R for about 77k, and adding 65k worth of upgrades. I added about 90k worth of upgrades, but I won ever race with a lead greater then 10 seconds.. By level 14, you should have 600k or so, and you can avoid spending any money by completing special cups, so this shouldn't be an issue. If you're good, and know what you're doing, you could probably do this in 6 hours, but I took 8 because I wanted to do some of the harder races for fun.

Also

Uncharted 1 - beat it in 7.5 hours on my first play through on hard. Did a lot of screwing around too. You can probably beat it in 3.5 hours on easy for minimum

Killzone 2 - 7 hours, it's noticeably shorter then Killzone 3, not the same length.

Metal Gear Solid 2 - Minimum 1.5 hours. On my second playthrough, I beat the game in 1.5 hours skipping the cinematics. This is for the PS2 version.