From what I've seen, we don't really have much evidence of his depravity except for the version of history written by the senate, and the senate had every reason to hate him given that he was actively working against them.
More can doubtless be written, but /u/Celebreth had a nice reply in "Was Caligula crazy? (subquestions)".
But this is not to discourage discussion -- further questions, data, and debate are welcome.