Obviously this has been dormant for a little while, but I've just re-watched What You Leave Behind for the first time in ages...
Endgame is okayish as a Voyager episode, but as a finale? No. The future stuff is too close to TNG's finale and the "Oh, we're home! Roll credits!" ending was unsatisfying. It also had some really bad dialogue. That said, I did love Alice Krige here, in fact I thought she was better than in First Contact.
What You Leave Behind is a strong finale. Stock footage notwithstanding, the big battle was exciting, as were the scenes on Cardassia. It also did a pretty nice job of giving the viewer closure as regards the characters, with nice moments such as Odo and Kira's goodbye, Ezri watching Worf leave etc. The flashbacks were pleasant if predictable, although, whatever the real world reasons, Worf having flashbacks without Jadzia appearing came off as weird. Alas, I really didn't like the Sisko/Dukat/Pah Wraiths stuff which felt out of place and tacked-on. The final showdown was unsatisfying and I thought Sisko had the worst ending of any of the regulars. Overall, it's very good, but it's not great.
All Good Things... has to get my vote as the best finale, even though I lean towards preferring DS9 as a series. There's something very fitting about the show ending this way - Q posing one last test for Picard. Also, unlike in Voyager's finale, I really loved the future stuff here, possibly because I just care more about these characters, but I also thought it was simply better executed. The way Picard moves between time periods like a regular Billy Pilgrim gave the episode an excellent structure and flow as well. It's a very satisfying ending, maybe even a little iconic and in my opinion it's the only truly great Trek finale (that I've seen anyway).