The original
Star Trek is the only series I still enjoy without reservations. I think it stands the test of time much better than all the other series, is much more dynamic and imaginative and isn't bogged down by byzantine continuity and hackneyed storytelling conventions.
Deep Space 9 had a lot going for it, including a terrific cast and, from time to time, truly ambitious writing, but as I grow older I can't take it as seriously as I used to.
There are some nuggets of brilliance to be found in
Enterprise, but they are few and far between.
I always hated
Voyager and I can't watch
The Next Generation anymore.