Hmm well if I remember our discussion rightly, or at least this is what stuck in my head since then: we mostly all thought the plot was thin. Like, a top-100 all-time movie needs to have more to it than just 'amazing dancing'. If that were the case, we could throw Fast and the Furious on there, just because it has amazing stunts.
I actually did like it ok, just not nearly enough to raise it over just about anything on this list so far (I have it at #82 of 92). The blackface, of course, doesn't help at all, and that probably is reason enough to tank it though.
Also I think the consensus was there are better films by Fred & Ginger too that aren't hard to credit; they could easily go on this list with something else. (I can't really speak to that, this is still the only Fred & Ginger film I've seen.)