I know this can turn into one of those Trek vs. B5 style arguments, but I'm just gonna say of the whole bunch I only like Highlander I and II, (Maybe its just Virginia Madsen, but I really like II ) the director's cut of II "renegage version" is the only way to see it though, the original version of II, with the aliens, was largely the product of interferance from the films Argentine money backers, who since they were paying, figured they knew how to make a better film. Lots of films in the 80s and early 90s suffer from that kind of thing.
Never watched the TV show.