Milligan WAS a genius, and I think, from the BBC4 documentary, a lovely and generous guy, who bravely broke the taboos about mental illness. I don't blame anyone for not loving his comedy, as when you're successful and creative, you pave the way for others to come in and do a fresher, newer version. The difference between Milligan and Monty Python, apart from the latter having six writers instead of one, was Python decided to do everything 'straight', not seemingly caring what anyone else is thinking, while Milligan and The Goons employed silly voices, slapstick and appealing to the audience.
Milligan and Sykes shared custody of a great joke which only they could use: "Spike and I shared and office for 20 years. We were very close. It was a small office."
My favourite Milligan moment was simply a 5 second sketch in which Concorde takes off, while in the foreground, a man's trousers fall down. It's kind of beautiful, though I'm not sure why.