First of all, characters and their relationships are essential for me to really love a show. Good stories are a close second. So here goes:
Enterprise: I like the cast and the chemistry was great in any combination and this show felt more like the original than any other. I admit, storytelling was uneven, but I loved or at least liked a lot more episodes than I didn't. The CGI effects were fantastic, as good as anything I ever saw at the movies.
Star Trek: The biggest draw for me here was the chemistry among the big three, yet there were also really nice scenes with the secondary characters. Again, I loved or liked more episodes than I hated. I really do have a soft spot for the original.
Deep Space Nine: It took me a while to warm up to the characters and many of the early stories might appeal to me more now that I have gotten to know and care about them. I will say the later seasons with the war was a great arc.
Voyager: As with DS9, I had to warm up these characters and boy, it didn't take me long to get bored by the Kazon. Also, early episodes rarely grabbed me and I know I'll get it from the Kes fans, but I much preferred Seven over Kes and I think the series got better with age.
The Next Generation: Sigh. I was SO EXCITED when I heard Trek was returning to TV! Then it premiered. I really didn't like the bridge (and what was up with the wall-sized viewscreen?!). Big isn't always better. It's just big. There were some characters I never got to like. I will say there were some fantastic episodes but when the stories hold more interest for me than the people, the show is a bit of a flop, IMO.