I've never seen Nadia, but I know that Atlantis is based partly off Jules Vernes' book, 20000 Leagues Under the Sea, even though Atlantis was not terribly important in said book. I believe that Nadia was partly based on that book, as well (as with many other things). I think people are just jumping to conclusions: they're based on the same source material, of course there's going to be similarities. Jeez.

I'm going to see it today (hopefully), and I'm really looking forward to it. I think I'll enjoy it. The idea of a lost, ancient city is so fascinating to me (one of the reasons why I enjoyed the Road to El Dorado so much), I'm surprised I've never written about it, actually... plus Michael J. Fox is my favorite actor, and he's voicing the main character. :D What more could I want?