I've been a fan of the original series since I was a kid in the early 1970's, watching reruns on WKGB Channel 56 in Boston on a tiny, grainy black and white screen. I built the AMT Enterprise and Klingon D7 models, and owned a Mego Spock action figure. TOS will always be Star Trek
Having said that, I think Next Generation was a worthy successor, and consider that my second-favorite series in the franchise. None of the later series really do anything for me, though I did have high hopes for Enterprise
when it went on the air in 2001, and was disappointed in how it turned out, like many of you were.