Apart from it being incredibly rude and tactless to a Japanese developer who'd paid his way to his first GDC, Fish's comment in isolation wouldn't really be enough to criticise him. But following that, his arrogant, self-aggrandising behaviour (that "suck my dick. Choke on it" business), not to mention what happened at the IGF - where he voted against the re-entry of another developer's game, only to turn around and re-enter Fez - would seem to demonstrate that he's not a particularly nice guy.
He's made a good game and he's right to be proud of it, but all that other stuff was so unnecessary. And while his comment about Japanese games might be broadly true, it could easily apply to games from any territory. Some would argue that most western games suck, too.
I think it was borne of a frustration with the apparent lack of (for want of a better word) magic in modern Japanese games compared with those that clearly inspired Fez; the games of his youth. Also, he's probably not played Vanquish and Dark Souls and Rhythm Tengoku and TWEWY etc. etc.
