If movies are being considered you'd then have to say that Nemesis was really TNG's finale since that was their last one and they all go their separate ways. But I don't think many TNG fans will buy that one.
As much of a downer as it is, I did like the moment where Riker recalls his first meeting with Data. A nice little nod back to the very beginning. It's a shame they didn't include the real
final ending with Picard's new first officer though, as it had a much more upbeat feeling, plus an overt reference to Farpoint station.
Certainly I think The Undiscovered Country
deserves to be considered as TOS's finale more than Turnabout Intruder