I dunno about it, on the one hand, it looks like some pretty cool sci-fi, but on the other hand thats a hell of a lot of CGI aliens and there just seems to be something not quite right about how its put together, like the human actors and the CGI ones don't feel like they fit together in the scene properly. Dunno if I'd just get over it while watching the movie and ignore it or if it would grate on me the whole time.
I've been getting through Cosmos very slowly, I think the episode I'm currently stuck on (it was the first sort of boring one) mentioned this as one of Carl Sagan's favourite childhood books. Heh, timing.
Looks awesome. CGI looks good, everything flows well. Not sure what you mean by Aliens stand out against John Carter, but it is CGI, you can always tell whats the real deal. Still, looks more interesting then Avatar.
Edgar Rice Burroughs wrote the original, 'A Princess of Mars' book that this film is based on in 1911.
George Lucas was inspired by this work when he made 'Star Wars', that is why this reminds you of 'Attack of the Clones'. That particular film is HEAVILY inspired by Burroughs Marian (and other) works.
Go read some ERB. It's great rollicking stuff; and all written in the early half of the 20th Century, long, long before anyone even dreamt of CGI.