GTAIV was lead on 360, and it was too hard to say which one looked "better". But the 360 version had a sharper resolution i think.
Burnout Paradise is slightly better on the PS3 but both look great which is how all the multi-plats should look.
But there is not one multi-plat game on the PS3 which blows away the 360 version.
The same cannot be said the other way round.
So yeh... 360 is going strong.