Yes, the game I swear I've seen many say ended up looking better that that CGI-rendered trailer.

Yeah I've seen a lot of folks claim this too which is insane. I think the final game's more stylised look with heavy post-processing kinda skews people's perceptions and smooths over the downgrades to characters, animation, smoke, modelling, etc.

You may be right. I haven't compared the trailer and the game properly, but they look very comparable to me. I took another look at a comparison video, and while some aspects look worse, some look better. Perhaps with a more in-depth look, one could reach your conclusion.

The CG trailer was rendered offline with unlimited render time per frame so it's not really a fair comparison, but stuff like the number of polygons poured into the characters, the billowing smoke and flames, etc are just way beyond what a PS3 could realistically do in a working game. 

The final game LOOKS more eye-catching in some ways not cos its more advanced, but because it leans into cool-looking tricks like colour grading, depth of field, bloom, etc.