A movie can only be as great as its source material. It can almost never be greater than the sum of its parts.
Here, the one lacking element was the screenplay, and it's a shame. The acting was superb and the direction took the script as far as it could go.
There were too many Asgardian minor characters. Sif, Hogun, Fandral, Volstagg, Tyr, etc. None has enough to do. It feels like there was more to the Sif-Jane-Thor triangle that was left on the cutting-room floor, which is a shame. It would have been better to drop any nods to the Warriors Three.
Another problem was the ridiculous hand-waving that got the Aether into Jane. The Portal-like... - well, portals were cool but there had to be a better way to release the Aether. Maybe there was a better way to drive the plot and forget the Aether completely.
Speaking of handwaving, isn't it a bit ridiculous that Heimdall didn't see the dark-elf attack coming? Isn't that his job?
It's a shame, because the small touches were all there. It was funny, adventurous, and unpredictable.