Well, its definitely not supposed to do that, that's for sure. Uncharted is one of the best looking games on PS3 to date.
I doubt it's your HDMI cable because you say all the other games work fine. Your PS3 should be fine as well for the same reason. So most likely there is something wrong with the game or the image transfer from the game to the TV.
It could be that your PS3 and your TV have some sync (?) problems. We had problems getting it to work with the TV all together when we first got it, then we reset the PS3 and suddenly it worked. Now, yours is already working, but resetting it might help.
I don't remember whether Uncharted needs an install before you can play it, but if it does, it could be that it did not install entirely correctly on your PS3 hard drive. Try uninstalling and reinstalling the game and see if that makes a difference.
If all else fails, it could also be that your Uncharted copy is just busted. Don't know where you got it, but you could try it on a different PS3. If it has the same problem, the problem lies with the game, not the PS3.
Good luck! Hope one of the above things solves it!