kangaroo - not impressed. I once asked an Australian about it, he said we don't eat it, we sell it to foreigners.
alligator - a bit dry, but it was on a pizza, they probably didn't know how to prepare it correctly.
bison/buffalo - very good stuff, I don't think it's much different to steak.
horse - could eat this every day
I'm guessing with ostrich, if you could get the thigh, it would be pretty good. The breast, a bit dry.