1
The games look better.
The fact is that very few Xbox games support the
HD resolutions of 1080i and 720p, but even at 480p--which is much more common among Xbox titles--they look better than standard-def. If you're gonna stare at something for hours, shouldn't it look good?
2
Garbage in, garbage out.
HDTVs look their best when fed as high-resolution a signal as possible--flip between standard Leno and high-def Leno to see what we mean. The same applies to games: your HDTV looks best when given high-resolution graphics. 3
Utilize that gear.
Any tech enthusiast's natural inclination is to use as much of their gear to the best of its ability as possible. Maximizing your gaming experience is a no-brainer and doesn't cost too much extra: just $20 or so for the HD connection pack.