Xbox 360 eh? I'm in the exact same situation as you. I'm looking at a HDTV simply for watching sports and playing 360. Remember that the 360 is natively displayed at 720p, not 1080i, but it will upconvert it.
Personally, I'm in the range of a 26"-37" TV. I'm looking at LCD TV's mainly because in the "official" Xbox 360 gamers guide, which I have, it has an entire article about every kind of HDTV. Here are the grades they give, with a "10" being the best.
LCD- "Don't let the listed cost fool you; LCD is expensive. The bottom end thousand-dollar units are probably only around a mere 23-inch size. A true living room LCD display (37 inches plus) will run you over four grand, easily. Cost, however, is the only factor holding LCD back from a higher rating. If you can afford it, this is the way to go. LCD is thin, lightweight, incredibly bright and vivid, beautiful, and unlike plasma, it won't suffer burn-in. For the ultimate in 360 gaming- and the quickest way to a second mortgage- go for an LCD HDTV." RATING: 8
DLP- "Essentially the succesor to those big boxy projection TVs of the previous decade, DLPs are relatively small (usually weighing less than 100 pounds with a depth of around a foot) and offer excellent picture quality. Most natively display 720p, making them a perfect match for the 360, and they have excellent viewing angles. They range from around 42 inches to 60 inches in screen size, and are probably the best bang for your buck. Make sure you get one of the latest-generation models (they seem to be advancing at a rate of about a generation every year or so) - the newer the technology, the better the picture quality. The only downside comes from the fact that a small percentage of people see a rainbow effect on the screen simply as a result of natural differences in their eyesight. Be sure to look at one in a store to see if you're among those with rainbow-detecting vision." RATING: 9
Plasma- "The first time you saw a wall-mounted, flat-panel widescreen HD display in a storefront somewhere, it was probably a plasma TV. A forerunner in thin, lightweight HDTV, plasma technology definitely has the size factor going for it; you can easily hang these guys up on a wall. And boy are they pretty. Unfortunately, they're not the best choice for Xbox 360 gaming for a couple of key reasons. First and foremost is the fact that plasma is prone to burn-in - more so than any of the other HDTV technologies. That means walking away from a paused game for an extended amount of time, or even an anchored part of a game's interface during a long play session, can cause "burn in" to the screen, leaving a permanent artifact. The other prohibiting factor is cost. Plasma is very, very expensive, and when combined with the burn-in factor, it's simply not the best choice for the 360." RATING: 6
CRT- "CRT is the fancy name for the good ol'-fashioned heavy TVs you've had in your home your entire life. They're now available in 16:9 widescreen aspect ratio and in HD, but the overwhelming majority do not natively support the Xbox 360's preferred 720p resolution, instead upconverting it to 1080i (or simply displaying 1080i natively, which all 360 games will offer). The good news is that CRT HDTVs are very affordable; a desk-worthy 26-inch widescreen set can be had for as little as $600. A decent-sized 34-inch widescreen falls in the $1500 range. The bad news is that widescreen CRTs don't get any bigger than that. The reason may very well have to do with the fact that a 34-incher weighs in excess of 200 pounds." RATING: 7