^They tried something similar to that before. It was whomever won a photo contest though. And, G2's will almost always win because that's what the majority of this site's users own.
So yeah, there is kind of a bias, but also it's kind of a majority rules thing. If it were changed often enough, I think for sure we could rotate some G1's and G3's and G4's.
But yeah, the way it is now shows two G2's and an ad for the NALM with more G2's on it, so it's probably time for a change.