Burnout and GTA are the only two titles that i\'m aware of that devs have obviously developed on the PS3 first. However, give the PS3 another year to mature and it\'ll probably be pretty even, that is, if total sales for both consoles even out. Seeing as some of Sony\'s big sequels coming out soon, that will probably happen.
I don\'t see PS3 becoming the dominant developer platform though.