I've been pretty lucky up until now in that most series I like didn't end up being ruined at some point. For some reason I never watched GoT or Lost e.g.
However, there is one glaring exception: Heroes. It went downhill pretty fast due to an writers strike back then. I don't even know whether or not I'd be into a remake, since superheroes are everywhere now and the whole superpower copying thing is basically in every series with superpowers ever. But still, there was something intriguing about the show and I'd like to see them try again.