It's disappointing that so many people disliked Enterprise. That was a not a bad series, even before the show got tremendously better in Seasons 3 and 4. While the show had its faults that it gradually corrected, I have a feeling much of the hatred is a mis-directed response to Star Trek Voyager and Insurrection/Nemesis, who really ran the Trek franchise into the ground. When taken on its own merits, it's a fine show that I enjoyed watching nearly every week with a cast I enjoyed seeing on-screen (who didn't have that annoying arrogance that most Star Trek series have where the characters seem to think they've "evolved BEYOND lesser peoples".)
I've stated my opinion on Star Trek elsewhere on the forums before. But since you brought it up...
Enterprise was a good show. I absolutely hated Season 3 though. The Xindi conspiracy was far too boring to dedicate literally every episode of an entire season to. That portion of the series was dull and plodding with little to no pay off. They should have continued to explain away the Temporal Cold War through the occasional episode instead. Aside from a season-sized mistep, the only other real problem was the final episode. I don't know of a single person who actually liked the finale though.
I liked Voyager. I've never understood why it gets so much hate. The characters themselves were a bit cheesier than they should have been, but it wore off quickly enough (except for Tom Paris). Besides, it had two of the best characters of the franchise: The Doctor and Seven of Nine.
My least favorite series has always been Deep Space Nine. I thought that the majority of the characters were dull, with the only real exceptions being transplants like O'Brien and Wolf, or the always under-utilized Garak. I felt that the show fell pretty hard toward the end anyway. It, like Enterprise, suffered from a terribly boring war story during the last two (three?) seasons. Add onto that the utterly ridiculous inclusion and validation of the Bajorian religion and it became pretty damn laughable by the finale.
Despite their flaws, I've yet to see a Star Trek series that hasn't been worth watching. Even the
Animated Series is worth sitting through.