Overhyping.
This isn't just a gamer problem, but it does tend to be worse among our community. Not a real problem, just a bad habit.
Elitism.
I'm not pointing fingers here *coughPCGamercough*, but seriously, this whole "we have more refined tastes" thing and "we're smarter gamers" just makes you sound like console fanboys but with an expanded vocabulary.
Sequel-phobia.
This seems to be an issue that's almost exclusive to this site. It's as if the number 3 is a dirty word or something around here (unless it has "Episode" before it -_-), and if it has more than 3 entries, not only is it "milking", but it automatically sucks. Don't go judging because of the fact that it's a sequel. Let it suck on it's own merits.
Penises/Tits/Sex stuff in customizable things.
If you give an online community ANY sort of custom making thing, guess what the first thing the idiots will make is... not really that much of an issue with good moderators, but there's always one...
Over-reliance on auto-saving.
Remember when the fact that you had to go to a save point was somehow seen as a legit complaint against Dead Rising 2? People say games are too easy, that there's no penalty for failure...speaking of...
Contradiction
We cry about stagnation, but when someone tries something different, we cry "stupid" or "gimmick" or "dumb" or say "why not go with what works?". Gamers keep saying they want more artistic and creative games, but they rarely sell well...