I think it's difficult to say what games are more considered as art since I don't understand art. I have no idea how to appreciate a painting myself, but I will look at them. This was also a problem I had with GCSE Art when my argument for getting a D was, "So what was the correct answer to get a C?" which all I got was a huge grey area.
I could still say Limbo, Shadow of the Colossus and Braid are very good looking games, along with Okami and Jet Set Radio, but to say it was art is something I'm not sure about, at least not in a high fidelity way. To say it's art is to look further than just the aesthetic and say the game is great.
Damn I'm so depressed.