Creativity. Honestly, I'll forgive glitches in games as long as my world is huge, creative and fun, and offers me a different way of playing games. But, creativity also has to be implemented well. Not necessarily 'polish', mind you, but sometimes people put original features into games in a way that just doesn't work. Like, for example, Mirror's Edge. Quite an original implementation of a concept and a different looking world to most of the ones out there, but it didn't make for a great game in practice.
But, then, I'm a games are art hippie, and, beyond that, I'm willing to sacrifice my gamerscore in order to play games that I think are genuinely good and different rather than simply splurge money on 100 different clones of the same basic concept. And I can't comment on Uncharted specifically because I don't have a PS3, but, from what I've heard, it's not only the polish that makes it appealing, but a creative implementation of a lot of old standbys that keeps the game fun and interesting. Just because it's been done before doesn't mean it can't be done creatively. Of course, I could be wrong, but I'm just giving it the benefit of the doubt, because it would be dickish of me to judge a game I haven't played.