It says 1080p is supported on the back of the box, but my TV says it's only displaying in 720p, why? My display setting have every resolution selected, I don't get it. 
 
When I'm on the XMB it says 1080p HD, when I'm played Uncharted 2 it says 720p.   
  
Why cruel world, WHHHHHY?!?!

Ok, this is what you do. Go to your Display settings in the XMB and unmark the 720p and the 1080i. Next time you start the game it will be in 1080p. 

silly question, HDMI cable from ps3 to tv? 
 
/me goes to check 
 
[edit] okay look at the "DEFINITION" gfx on the back of the box more closely. It states "480P, 720P, 1080i, 1080P" with 720P bolded in red. 

" @SJSchmidt93: Your welcome. The PS3 is kinda weird about the display resolution. For example, Some games, like inFamous will only display in 720 and if you have the 720p marked off in the display settings the game will revert to 480p, but Killzone 2 says on the box that it only goes up to 1080i but it will run at 1080p. I think the reason for it is that eventually Sony wants all games to run at a native 1080p.   btw, did it work? "

Yeah the box defiantly says 720p

What's written on the back of the box has generally has no correlation to the actual rendered output of the game. Very few games on either platform are actually natively rendered at 1080p (1920x1080) infact you can probably count the number of PS3 releases with native 1080p on one hand (GT5P, Wipeout HD.... I guess thats about it not including a couple of PSN games). All your essentially doing by unticking the 720p and 1080i options is then upscaling the 720p source (similar to say blowing up a small photo in a paint program) via a software based upscaler. You will also find that in some cases you will receive a 480p source instead of a 1080p upscaled source (ala inFamous). This is normally due to a game being rendered at a resolution bellow 720p (1280x720) for whatever reason... normally when a developer will drop the resolution of a title to keep the frame rate consistant if they cant optimise their code any further. The PS3 then seems to default to rendering the game at SD instead of upscaling the image... dont ask me why just seems to be the way its designed. Anyway long story short, your not missing out on anything by having the ps3 rendering the game natively and having your TV handle the upscaling... infact as the PS3's scaling is software based not hardware based like the 360's youll likely remove some small amount of processing overhead which could impact your systems over all performance.

" Ok, this is what you do. Go to your Display settings in the XMB and unmark the 720p and the 1080i. Next time you start the game it will be in 1080p.  "

" Anyway long story short, your not missing out on anything by having the ps3 rendering the game natively and having your TV handle the upscaling... "

I was confused about this as well, but then I saw the "720p" highlighted in red. So that cleared up a lot of fog.