ps3 exclusives will always have the best graphics. Gears of War 3 will probably coming in 2011, almost a 2 year gap btw it and UC2, but honestly i don't think that it can have better graphics then UC2. I don't think that any game on xbox can beat UC2 their engine isn't capable.
PS3 has a superior engine, GOW3 which has the best graphics to date only used 50 % on the engine, so future PS3 excluvies will possibly reach 70 % and 80%, i really can't imagine how the games will look.
Being in 3rd place never felt so good