well...really cant say much..
This flash could have been delivered so much better than it was.. You just seemed to get very lazy at parts like the chuck norris part. However funny that was to me, it was just flat out lazy animation. And a very lazy drawing. You should work more on adding detail to the people who stayed in the fight throught most of the movie, like godzilla. He should have had at least a scaley body since you used him so long.
Batman just...needs to look more built, with his cape adding more of a dramatic effect to his movements then you made. I dont think the art style fit with this particular song, and this movie, like so many others, is not quite worthy of its score.
I am not going to say it was a bad flash, overall I enjoyed it, mainly at the end where the animation noticably improved. I guess next time just try harder to add detail, otherwise your doing just fine.