I'm not saying that you are. I'm just saying that the Xbox at 480p is about as good as it gets right now and if that is dissapointing there is nowhere else to turn outside of a home theater PC. Personally, on my 55" Mits I think the picture is fairly good but if I choose to really examine it the lacking areas are fairly evident so I totally understand when someone says they don't like it. I'm not passing judgement, it's simply a matter of what someone's eyes are drawn to (i.e. people sensitive to jaggies can go so far as to use Svideo and 480i on the Xbox sacrificing sharpness and color just to smooth them out).
If the dark scenes are the primary concern, those games are the same on all televisions providing they are setup properly (AVIA or DVE for brightness/contrast etc...). I don't know whether the people making the games have their monitors blaring or what but when we discussed it before it affected all of us on a variety of displays. Some people choose to up the contrast or brightness to help but I can tell you that I calibrated my Xbox input directly from the Xbox with a modded 480p version of the Xbox DVD player (hex edit on a modded box). It's setup correctly and some scenes in Halo2 and other games are just too damn dark. It's not the display, it's the games. I have no idea why they do this but at times I pause gameplay and adjust my settings so I can see - and yeah, I'm irritated by that.
Panasonic 65" VT60 (calibrated by Jeff Meier), Marantz 6005, Kef Q towers/rears Kef Reference center, Win 7 Pro with XBMC, Harmony Ultimate One
Xbox Live: Arbitrage XXL