Mike Henry definatly deserves his own series. Clevland does not.
You know what they should do, they should make "The Clevland and Quagmire Show!". However, That would make 3 series Seth Macfarlene would be working on in dual roles(he's going to write for Clevland Show), and that would probably be way too much work for him.
BTW, I think we should all be happy that Mike Henry's other character wasn't picked for a spinoff (Herbert)
and Darklordaviator, 2 Episodes weren't aired and it hasn't been announced it was renewed (It prolly will though)
But honestly, this sounds a lot better than King of the Hill, which should've been cancelled ages ago