I definitely wouldn't expect the same battery life as your iPhone 4, solely because the SGS2 has a much larger display. But having said that you should definitely get a bit more out of it. The problem probably comes from all the bloatware running in the background and the only thing you can do about that is root the phone and freeze the apps. I agree 100% that you shouldn't have to turn off a bunch of stuff to make your phone last, whats the point???
But a few tips:
-Turn on auto brightness, or turn the brightness down.
-Sync secondary accounts less often. I have my facebook and secondary emails synced every hour where as my gmail is as often as it can.
-Turn down the screen time out (15s-30s).
-Black backgrounds are suppose to help since SAMOLED don't turn anything on for blacks (which is why blacks are amazing on this phone).
I don't know what my battery life really is because I do charge it whenever I can but I can go pretty long with moderate use (not a full day but a good 12-16 hours).