My five favorite Simspsons episodes
"22 Short Films About Springfield". The stories about all the minor characters were great, and I particularly like the Pulp Fiction parodies that they toss in.
"Homer the Great". The song the Stonecutters sing is definitely the best song in the history of the show and there's a great pointless Last Emperor bit. To say nothing of the Patrick Stewart cameo
"Sideshow Bob Roberts". Fun stuff, especially since both political parties are exaggerated for amusement. The Sideshow Bob episodes are all pretty good (especially the Cape Fear parody), but I like this one slightly more than the rest.
"You Only Move Twice". Never mind that Homer's football team went on to win the Super Bowl a few years later. The combination of moving to a new town, a futuristic house, and a bizarre secret agent/supervillain plot is a winning setup. They actually kill James Bond!
"Marge vs. the Monorail". Okay, so I mostly remember this one for the song, but it's still one of the best from the early seasons.
Additionally, my favorite Halloween short (from my favorite Halloween special), for that matter) is "The Shinning". The "No beer and no TV make Homer . . . something something" scene is an absolute classic, and it's even better if you're familiar with the movie upon which it's based.
One is from season four, two (plus the Halloween short) are from season six, one is from season seven, and one is from season eight. Seasons three through eight hold the bulk of the show's brilliance, and my pick for when the show started to go downhill is the spin-off showcase at the end of season eight. The earlier episodes actually get better the more I see them (even the fifth or sixth time), but some of the later stuff is downright bad.