I wish I could have gotten into Deep Space 9, but I was kind of turned off by the stationary nature of the show... Being that it took place on a Space Station =P
Mostly I found that many of the episodes were often about the same thing, and I already knew ahead of time what the outcome of the situation would be, but they would spend multiple episodes getting there instead of just one. In the end I felt a little unmotivated to continue watching. I would like to have watched more of the show, because it had some interesting characters; but I wish there was more variety in the episodes. All in all, I found Deep Space 9 to have a very limiting format.
My favourite parts of the Star Trek series are Voyager from Season 4 through to the end of the series, and the entirety of Next Generation. 7 of 9 first appeared on Voyager during a Borg encounter beginning in the Season finale of season 3 and the beginning of season 4; I felt 7 of 9 and the Doctor combined on Voyager offered the most interesting version of the Spock type character - mostly because they split the character into two, and developed that storyline much more deeply than they did Data in Next Generation, and Spock in the original series. Voyager had an interesting formula, but was very adventurous, and was not at all limited by that story.
The Next Generation really seems like the concrete foundation for the Star Trek Universe - one thing I liked better about it was that it managed to achieve more in some 3-4 episode mini-stories than Deep Space 9 achieved in multiple seasons. There were some episodes that were just completely brilliant: like the one where Data created Lal.
My favourite movie of the Star Trek franchise was Star Trek 6: The Undiscovered country: while I felt the Borg was the best villain entity in the series - in my humble opinion: Star Trek 6's shaved head Klingon General Chang (played by Christopher Plummer) was the best villain of the Star Trek series; I never understood everyone's attachment to Khan, maybe he is a bit before my time. My least favourite was Star Trex 10: Nemesis... I don't recall the movie THAT well, but I felt the 11th Star Trek had many similarities to Nemesis, only it was MUCH more entertaining - and having the most iconic characters present was certainly a major plus.