The trouble with Highlander was the sequels. The movie ended perfectly, tying up the story and leaving it closed. Of course when sequels were made they just stank because they were trying to add to a story that was for all intents and purposes was over.
Of course the franchise has been rebooted before (twice).
The was the television series that starred Adrian Paul as Duncan McLeod and that worked well, stumbling to start with but growing into something rather good by the end. However once they tried to stretch the premise onto the big screen it lost itself completely.
There was also a cartoon series that feature Quentin McLeod and although I never saw it, the reviews at the time were very positive.
The trouble seems to come when they try to stretch the whole concept, trying to extend 'The Game' and go beyond the whole 'there can be only one' idea.
So I'm quite sure rebooting can work. If they plan it well enough, with an end to aim for and stick to they might get something special, but the second they try to go beyond that it will struggle.
(It also might be said that it will have to be a different beast to the original. That was one of those things that should not have worked, it just did as all the elements came together. Christopher Lambert, a Frenchman playing a Scott, Connery playing a Spaniard, who was in fact Egyptian with a Scottish accent, the soundtrack by Queen...)