The Next GenerationS7 All Good Things
All Good Things is the series finale a feature length/two parter episode which bookends the seven seasons magnificently and considering that Q was put into the premiere to pad the episode into a two parter it's quite an achievement that it all worked out in the end.
May I say Gates McFadden also looked spectacular in the episode and was perhaps the best made up for her characters older self, subtle and far more convincing that some of the guys, Patrick Stewart of course can look almost any age you want:)
A truly fitting finale to The Next Generation, wonderfully produced, expertly and tightly written making full use of the cast as well as mixing elements from the entire run of the series. I'm hesitant to say it's the best finale since the DS9 climax was really an epic multi-episode arc but lets go with All Good Things being the best standalone finale from Star Trek.