I’m thoroughly enjoying the Halloween episodes of Bob’s Burgers. I haven’t watched the show before - think I’ll start - but these are really fun. The Simpson;s Halloween episodes are classic. Modern Family has a few. Buffy. Everybody Hates Chris.
What favorites am I missing?
Addams Family had one with Don Rickles.
Star Trek even had one with a witch and a giant cat.
Roseanne had a lot of Halloween episodes. They were often good.
The Simpsons Treehouses of Horror are a from good to great.
Community has the Zombie Halloween party, it was awesome. They had another good one at Pierce’s Mansion.
Gravity Falls took place over a summer, but they still managed to have a fake Halloween episode called Summerween, a summer version of Halloween. It’s fun.
Community:
Charlie Brown:
And The Conners continued the tradition.
Home Improvement
The Season 4 episode “Home” from the X-Files is supposed to be the most Halloweeney of all the episodes.
I know of, “Halloween is Grinch Night,” but I can’t make myself watch it.
The original Quantum Leap had a creepy Halloween episode
Alien Nation the Fox-TV series in '89-'90 had a Halloween episode called “Night of the Screams.” Apparently the human pagan festival happened to coincide with “the third equinox”, the time of Tagdot, the Taker of Hands…
The sitcom The Middle had eight Halloween episodes in their nine seasons. The are very creatively (not!) named Halloween I through Halloween VIII. They were among my favorite episodes of the series
I recently did a binge watch of Brooklyn 99 on Peacock. They did an annual ‘Halloween Heist’ episode. It began with a bet between Andy Samberg’s character Jake and Captain Holt over who was a better detective, and took the form of the Captain locking away an award of his, and Jake would use tricks and subterfuge to try to ‘heist’ it.
It grew to involve the entire precinct, and became a very complex annual episode over the seasons, with comedy take-offs on a number of movie heist tropes: layers of fake-outs and twists, broken and crossed alliances, crawling through ducts, etc. etc.
It seems that, in their part of Brooklyn, they had much less crime to deal with, and much more downtime than one would think 
I recently watched a retrospective on the “Family Matters” Halloween episodes.Apparently the first “Stevil” episode (where Steve Urkel has an evil ventriloquist doll after him) is actually pretty scary for a sitcom.
I was going to mention the The X-Files episode with Ed Asner and Lily Tomlin as ghosts, but I now think that it may have been a Christmas episode rather than Halloween.
Buffy the Vampire Slayer had some good Halloween episode, including one called “Halloween” when the people were turned into their costumes.
It wasn’t a Halloween episode per se, but I think The Monstrous Monkee Mash (S2E18) should qualify.
Davy has been put under the spell of Lorelei, or to be precise, her magic necklace. Her uncle, a Transylvanian Count, wants to turn Davy into a vampire. When the other Monkees arrive looking for their missing mate from Manchester, Peter’s mind is singled out to be put inside a monster and Micky to become a wolf man. Mike manages to escape the vampire’s clutches by dressing up in a mummy’s smelly old wrappings.
I vaguely recall Night Court having interesting Halloween episodes.
Freaks and Geeks had a decent Halloween episode, complete with Joe Flaherty’s character in a vampire costume (get it?).