I have seen all of the finales, even though I've only seen like six episodes of "Voyager" and 4 episodes of "Enterprise". Here's how I would rank them...
1) "All Good Things..." - It had a suitably epic and original plot, and at the same time featured plenty of lovely emotional moments and interactions between the characters. Really showcased all the best things about the series, ending a seventh season that had done the same thing very rarely.
2) "Turnabout Intruder" - I guess I'm in the minority here, but I seriously thought this was a great finale, even though it (ironically) wasn't even meant to be a finale. People complain that it's sexist, but I never saw it that way as I was watching it. I just thought of the female guest star as just another one of those individuals/groups/forces invading the Enterprise that appeared during the series, and one of the more interesting and entertaining ones.
The episode also had a lot of my favourite recurring qualities of the series. Along with that 'invader' character, there was an awesome performance by William Shatner as Captain Kirk possessed by someone evil, strong supporting turns by Nimoy, Kelley, and Doohan (!), and a nice wistful ending, which gave the episode a perfect sentimental moment and line of dialogue to end a series on.
3) "What You Leave Behind" - While the series finales of "Star Trek" and "Star Trek: The Next Generation" demonstrated some of the best qualities of their respective series, this truly was the best and worst of DS9. A maddening finale that, much like the new movie, went back and forth between excellent and horrible. All of the events leading up to resolution of the Federation and Dominion conflict were spectacular, and the celebrations and farewells between the characters in its aftermath were wonderful.
The final montage actually made me WEEP with nostalgic joy, something no other episode or movie of any Star Trek series has ever done (although a few have given me the watery eyes). If this was all there was to the episode, I would definitely rank it higher than "All Good Things...", but in between all those fantastic moments, the episode kept cutting back to the nonsense with the Dukat and the Pah Wraiths. Then the final insult was following up the beautiful montage and Vic Fontaine's heartwarming song with the absolutely pathetic Dukat and Sisko confrontation. I've never seen an episode blow it so immensely. There is so much brilliance on this show, it's too bad they pissed it all away.
4) "These Are The Voyages..." - I knew next to nothing about "Enterprise" when I saw this, and I was happy to see Riker and Troi again, so I didn't mind it. I did feel a little cheated that they kept building up to Archer's supposedly amazing speech and then we never actually heard it. Such lazy writing. I won't defend this episode...I can understand why other people loathe it, but as a TNG fan who doesn't care much about "Enterprise" and its characters, maybe I'm the only person with the background to think it's passable.
5) "Endgame" - Well, I hate "Voyager" and every character on it (except I kinda like Tuvok 'cause he sounds like Spock), and the finale didn't change my mind about it. I only ever enjoyed this show when Q guest starred on it and his natural charisma gave the other characters a much needed boost (they've always seemed boring to me). Unfortunately, there was no one in this episode to keep it from being just as boring to me as any "Voyager" episode I've seen that didn't have Q in it. Alice Krige was terrific as the Borg Queen in "Star Trek: First Contact", but I found her just as mediocre and forgettable on this show as the rest of its cast. I'm trying to block out the memory and forget she's ever appeared in any other Star Trek production besides that movie.