SGS winning features
- better camera picture quality(altho no flash)
- best GPU available (3D games will run very very smoothly)
- nicer and larger screen

Desire's winning features
- android 2.2
- more solid feel to the body
- sense UI
- camera flash

honestly, i tink the the galaxy S has a better chance to survive in the future, because mainly of its GPU and its proper multitouch(not the 2 points multitouch).. when and if better quality games come out, u will be able to play it without a problem.. coz the newer and upcoming HTC fones will mostly come with the newer versions of Qualcomm processors like the scorpion, and the scorpion will haf a much better GPU than the current sad GPU of the snapdragon..

so it only depends on whether u want to play 3D games on your fone, if you dont, then u can juz go for the desire. but if u do wanna play 3D games, then its a no brainer to get the Galaxy S.