Just as it didn't matter with Halo 3 on 360, it doesn't matter now. There's more to graphics than the resolution. Halo 3 ran at slightly lower and made up for it with lighting effects and some of the textures, in order to keep as much stuff on the screen as possible without dropping frames. GTA IV on PS3 looks better in some aspects because dropping the resolution allowed for some better effects to laid over the top.
They are different systems and will have different specs on different aspects. The side by side videos look very comparable, with some slight differences - some plusses for each side.
When it comes down to it, if the game is fun and there are no crippling deficiencies on either side, it really doesn't matter. Judging from the 10s dumped onto both platforms in reviews, this converstaion is kind of pointless.
Can't we all just get along and play our games in peace?
