Well, I think Betu had the best answer so far. Looks are subjective -- we each have our own "type," so it's pointless to remark on physical qualities. A good model is one who performs well. Someone natural and not forced or fake. One of my biggest pet peeves is the fake porn sounds and dialogue -- I HATE that. It sounds stupid and distracts from the scene. No one needs to be saying ridiculous canned porn cliches like "oh, yeah" over and over again, or "do you like that cock" and silly things like that. Natural heavy breathing, moaning, and the occasional real comment are plenty -- we aren't watching this stuff for the dialogue, so there's no need to over do it! The same for the plunger kissing -- that noisy, sucking/popping crap. Fake and stupid. Unnecessary. We can SEE models are kissing, we don't have to HEAR it -- who really kisses like that? But I digress....
So I think good models are just guys who are themselves, honest and sincere, and confident enough to try new things.
Kaden Alexander is a perfect example -- it seems the forum members either love him or hate him. But no one can deny that he's really evolved as an adult ENTERTAINER. He tries to make his scenes as good as possible, is always professional, and so far has been willing to give pretty much anything a try. I am one of his biggest supporters -- I LOVES me some
Kaden Alexander -- but that notwithstanding, I don't believe he's ever done a scene that has really flopped. Models who are confident and can back it up with their actions and not just their words are those who are the best performers.