It's hard to say as the 360 isn't out yet. Most die-hard gamers still swear by CRT sets, and for CRT's you probably can't beat the Sony KD-34XBR960. Check out the CNet review of the set. But, if you have a favorite technology other than CRT, then you will probably not be disappointed by it's gaming capabilities, up to 720 pixel resolution.
The new 1080i resolution sets coming out now will be able to full display the Xbox 360's high-res capabilities, but I wouldn't expect a ton of games in resolutions over 720p any time soon. If that holds true, then most HD sets, whether they are LCD, Plasma, or rear projection will be able to show all the detail of these games, and most can accept a 1080i signal and display it at 720p.
The Sony 34XBR will display resolutions even over 1080i, so that isn't an issue. If a giant 60 inch display isn't a priority for you, and you can handle the huge size of the tube, that may be your best bet. It (or something similar) is probably what the Microsoft guys use to develop the 360.

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