It is what the sequels should have been and it gives justice to the original.
The first season is weak. It borrows the antiques dealer riff from the movie and most of the plots are the standard women-in-peril thing that we are probably all sick of. Tess is in danger, Duncan has to save her. Repeat, repeat, repeat.
Even then, however, it still had its charm. It picks up when they move the location to Paris and from then on the writers have clearly found their footing.
The Second season starts with a bang that can be heard from the first episode on. They drop the woman in peril thing entirely, they add a protégé for Duncan to train. He swaps the antiques business for a dojo and the story starts to really move along at a breakneck speed.
By season 3 and 4 you should be locked in. The supporting cast has been well developed, everything is chugging along nicely and cemented enough for the plot to really thicken. They aren't reliant on the old tropes anymore and the fat has been trimmed enough for you to get at the real meat.
It doesn't really go down hill until the final, abbreviated, season when it became clear that Highlander did all it wanted to do and they were just out there looking for a spin-off. The series itself wrapped up nicely in Season 5. Season 6 was just an attempt to launch a new show.
Ultimately what you have is 4 stellar seasons, with the first season hit or miss, and the last season clearly not intended to continue the over-all plot of the show.
