I LOVED IT SO MUCH. I won't say it's my favourite (Captain America: The Winter Soldier was amazing on every level, and is hard to beat), but it was great.
My one criticism
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is that the plot seemed a bit thin, but that's just because there was so much information they needed to get across, that the reasons behind the conflict were not always clear. Why Ronan wanted to kill the Xandarians was only expressed in throwaway dialogue. But I had the same problem with Thor: The Dark World, and subsequent watchings of the movie cleared that all up.
But otherwise, AMAZING.