I thought Battlestar Galactica had a decent (but not great) ending. However, while I've met people in real life who agree with me, I seem to be the only one on the internet who feels that way.
Lost's ending had me regretting all the hours I spent on that show.
Newhart's second series, the one with the hotel in Vermont, had possibly the best series ender ever.
Cheers was consistently good: it went downhill a bit, but never fell off a cliff/ jumped the shark.
The ending of The Wire was OK but a little disappointing: the way everything ended on a cycle, with old characters moving off and new replacements moving in, was tidy in a way that seemed against the spirit of the show.
I think the ending of The Sopranos was brilliant.
I've been told that Six Feet Under is worth watching simply for the ending. Still haven't got more than a few episodes through the first season, however.
Oh, back in scifi land (which may not be to your taste): Deep Space Nine progresses and wraps up pretty well, but it suffers from having too many episodes in each season.






