Our intuitions about the matter seem to depend on whether we think of it as creating an uplifted chimp or a retarded human.

You don't know whether the result will even be a uplifted chimp. I think there a fairly good chance that gene's won't be expressed in a way to make the result more intelligent than a chimp if you just randomly combine gene from two different specis.

You could learn a lot through the experiment but I doubt, that expecially at the beginning the resulting creature would be very intelligent.

Recreating neaderthalers as is seems to be a much more interesting ethical question.