Babylon. Play for 100k culture. You'll be pleasantly surprised at all the cheap buildings. Their UU is mediocre or even bad, but that is not their real strength.
I'm a little confused. With the cheap buildings for all cities, it seems Babylon would do best for a 20K victory? Although they're a little better at 100K, 20K would seem to be their specialty. Am I missing something?
For conquest or domination, I think it's about even. Neither is ideally suited to that victory condition.
For Space, maybe Babylon?
This all assumes C3C. If it's vanilla, Egypt would be my choice for all except 100K.
i always play conquest/domination games