Yes you can't find pics where Vita games looks as good as PS3 games. You can even take some good pictures of some 3DS games like
Resident Evil Revelations and it will look better as some PS3 games and Vita games.
But if you see the Vita games in motion they fall far behind PS3 games.
The PS3 has some impressive technical components (mainly Cell-CPU) but fails on other components as GPU and technical design choices like half RAM for GPU/CPU, so the Cell power was wasted. The same can be said for Vita. Vita has some nice technical details on paper but in real life Vita games looks disappointing for a "PS3 on the go". Games that are made to look graphical impressive, like Uncharted or Assassins Creed only use half resolution on Vita (thats 3DS Main-Screen resolution!).
Till today Uncharted is the graphical most impressive game on Vita. Assassins Creed and CoD looks surely disappointing. Even one year after its release there seems to be no improvements on Vita graphic engines (same is true for 3DS). And the only company who will take enough money for production to use the capabilities of the Vita will be Sony, because Third parties don't see money in Vita games. And Sony has, as we all now, not much money left these days. Will they invest in Vita or PS4? I don't think they have the chance to support both plattforms.