I never really thought about how disparate the component parts of this franchise has been. Nothing goes together very well though I think tonally II and III kind of go together.
I actually sought out the pre-Renegade version of Highlander II because that is so gloriously bad it should be appreciated unadulterated. The first movie while cheesy is fun 80s adventure.
Never liked the series though, I can see why people do but I never could get into its tame syndicated form. I remember the cartoon being a very odd French toon barely recognizable from its source, don't really recall if it was good or bad though, I don't think I was open-minded enough at the time to get past its digressions.