He's quite full of himself (the show was called "Seinfeld" after all, before hardly anyone recognized that name), but I think that's part of the comedic persona, that's his routine, a snob successful man.

A thing I really find off-putting is the overt misogyny of the Seinfeld character in the series - he's a ladies man and has very little regard or respect for his romantic conquests, over 70 throughout the series, iirc. Jerry's love interests are a source of gags, but the fact that he's essentially a sexual addict if never addressed or mocked.

I realize the character is not the same as the comedian, but it's hard to disentangle the two, especially if he owns up to such a large influence on the final text. It's as if a woman was never involved in the writing so she could object to the disposable nature of Jerry's female companions. Is it a personal fantasy that's being projected, is it a comedic version of his real life? I don't know.