I was tempted to vote Lost, but I think my disappointment started long before the finale. At the time I was really disappointed with the Seinfield finale but now I'm not so sure if it was that the episode was that bad or that it had an impossible level of hype to live up to.
The finale of Sopranos was perfect and retched all at the same time. The show spent all those years keeping me on my toes, because the violence and personalities were so unpredictable, and that ending just made the uncomfortable tension permanent. I mean, yeah, I didn't like it, but I can't argue with the effect. The characters live in a place where the end can come at any time, and in any way. Just like I'm left in limbo wondering just what the hell happens next, so are they. The lifestyle never ends. I think that's a brilliant move.
Cheers is one of my favorite finales for exactly the same reason. I know they are all still at the bar, still doing the same things. That makes me happy to think about.
Lost, just... just Lost. It felt like they revealed the worst things, the mysteries that didn't need answers, like the source of the echoes. What we needed to understand was why the island was so important, what would have happened if it were destroyed and why it was wrong for Barry to leave the island. There's a theory that if the island were destroyed, the ability for people to reach the afterlife would have been destroyed and with it, faith and religion itself, which would have been an interesting motivation, but they could have told us, or at least alluded to it better.
Lost was totally botched. What ended up being true in the finale was exactly what the people behind that show said wasn't the case all along.
It left me feeling cheated. I sort of regretted watching the series after that. It had so much potential to be mindblowing too.
Sopranos too...while I have more respect for how they ended it vs. Lost, they could've done a lot more with it.
I actually enjoyed the Seinfeld ending. Still one of our favorite shows.