The only two finales which are worth rewatching are all good things, and What you Leave Behind. As Lieutenant Q pointed out, turnabout intruder was not intended as a series finale, and even if it was, its still one of my least favorite TOS episodes. Having Kirk's psycho ex-girlfriend switch bodies with him, and go around the ship throwing tantrums was stupid. The only redeeming quality of the episode, was watching Shatner walk around filing his nails. Voyager was my least favorite Trek series, so noone should be surprised with me not considering the finale to be the best. I liked Enterprise as a series, but I though the end was pretty weak. Of the two that I liked, I would have to go with DS9. Although it got a little Star Warsish at the the end, I thought it did an excellent job closing the dominion war story arc. The one thing I disliked about it, was that they set up a brilliant concept with Sisko not having a linear life, but failed to use it. It would have been interesting to have him show up for an episode of Enterprise for instance.
If we're discussing the pilot episodes, I think Emissary, and Broken Bow were the two best ones. Encounter at Farpoint like most of the early TNG was kind of weak, Caretaker was okay. The Cage, and Where No Man has gone before were both good episodes, but suffer from the fact that they were only one parters rather than two hour premiers.