u can forget about SGS as it don't have even LED flash. not really great for photography.. I'll chose Nexus S as it is newer model than all those. it also got the superAMOLED entertainment purpose, sure it is able to handle them in no problems with the A8 1Ghz processor. It also got the rare front camera on android
DHD also good.. but superAMOLED sure win the S-LCD. only plus point for DHD IMO is the large screen. if u use to browse net a lot, DHD is better for the larger screen, provide u with comfortable web surfing. but since u may do web browsing a little bit less, i think, Nexus S suite u better there. hope these help at some point

I have "downgraded" from Desire's Amoled to Desire HD's TFT.  I will never look back to my Desire again. 

Seriously the sheer size of the DHD really make up for the loss of higher saturated AMOLED.  Once you get used the new screen, trust me, you won't want anything smaller ever after, no matter what AMOLED lah... Super AMOLED lah... unless it is 4.3" AMOLED or SuperAMOLED....lol...