Good beginning, lousy ending
All in all, it's one of the less disappointing modern Disney films -- up until the midpoint, when Roarke does his heel turn.
Up till that point, it was quite interesting. The campfire backstory chat was way too long, but there was good material otherwise.
Milo, the lead character, was very sympathetic and had a fine introduction. The premise of the plot, with the book and map and all, was very Indiana Jones and the Last Crusade, but not too slavishly a copy.
The native princess was fascinating and fairly attractive. The budding romance between Milo and the princess was very engaging.
The character animation was a bit blocky, but not as bad as in some other modern Disney films.
The design of Atlantis was breathtaking.
However, after the midpoint, when the bad guys do their betrayal, everything becomes pretty awful pretty quickly.
Of COURSE the two white mercenaries, Roarke and the blonde, are the "evil" ones, while the ethnic characters turn out to be good. Typical political correctness.
The metaphysics with the power source and the gems was very murky, something vaguely spiritual and vaguely eco, but not at all compelling.
Turning the princess into the conduit of the power removed the most interesting character apart from Milo from the plot for a good chunk of the action, right when we wanted to see more of her.
The entire action sequence was standard Hollywood fare and actually kind of routine. No surprises in it at all.
Learning more about Atlantis would have been far more interesting than what we did get. And, for that matter, seeing more of the Milo/princess romance.
Ultimately, a great beginning let down by a very poor latter half, or at least a poor third act, depending on where you place the point of the Roarke heel turn, time wise.