If this was about the most remarkable PS3 games (subjectively) or my favourite PS3 games, I might answer otherwise, but of the ones I've played so far, I believe one rises above all others to be the best: Uncharted 2. I don't think it's even a close one, but do keep in mind that I've certainly missed a lot of games, played many PS3-era games on PC only, and if there are games that don't appeal to me all that much even though they're (somewhat) objectively speaking great, I'm not going to bring them up in a discussion like this.