In your opinion, what are the best/your favourite simpsons episodes of all time and why?

The movie ;)

The monorail episode, only one that actually made me laugh.

It's not a full episode but "The Shining" (pronounced Shinning) was my fave Simpsons bit ever.

The very last episode... ever! Seriously, I'm surprised that this show is still alive and kicking. I think they should have canned it years ago. Oh well.

It's amazing isn't it?
Personally I think it just goes to show how the majority of the networks prefer to stay safe with meh shows.

Too true. Sure, I used to like the show, but it has changed so little it has simply become bland.

The Simpsons Pinball Party, on the other hand, is still great fun. ;)

I think I can narrow it to down to Season 6 having the most of my favorite episodes. Homer Badman, Lisa on Ice, Homer the Great, Homie the Clown, A Star is Burns, Lemon of Troy. Even crappier episodes in the season like Lisa's Rival have hilarious sub-plots like homer stealing sugar from an over-turned truck and trying to sell it.

It's hard to pin down. I liked moments from seasons 13 - 17 the most. I guess, I never watched it in order. Episodes had a plot and a great mix of subtle and in your face jokes about real life. In general, it has made me laugh quite a lot till Season 18 or 19.
Watching the last couple of season is like looking at a panting old horse hobbling to the finish line. An episode is either plot completely borrowed from a famous movie/book/series only with redrawn characters or retold story from another country authors probably don't know much about and thus keep joking about one stereotype tied to it. I watch it out of habit now.

EDIT: To be concrete, I would say Co-Dependent's Day (Oktoberbest), Lisa the Vegetarian (Slaughterhouse Tape), the episode where Lisa outwits saleswoman with Dolphin Doctor and the Tomacco episode.

the one where that dude said 'eeeey' and did that one thing i was like "lol" and homer was all "woohoo."

The one that springs to mind is 22 Short Films About Springfield.

Hell, yes, that one where Homer chokes Bart, right? The best episode ever, hands down.

Cape Feare. The one where Bart's placed in a witness protection program and The Simpsons are renamed The Thompsons due to, who else, Sideshow Bob.

It's the H.M.S. Pinafore scene that clinches it for me.

This was before The Simpsons conceded its status as a cartoon (meaning they were still somewhat concerned with maintaining some realism) and so that whole sequence just makes me imagine Bob rifling through the boat's broom closet to find props. Then the whole thing goes out the window as soon as he's presented wearing a full captain's uniform.

"I will send you to Heaven, before I send you to Hell!"

Too bad I can't find a decent quality video for it. :(

As a consolation, I've promised myself that if I ever win a public office I will laugh like this during my inaugural speech.

I am by now means an expert but the episode where George Bush Senior becomes the neighbour of Homer is my personal favorite.
It's this one: http://wtso.tv/movie/85-The_Simpsons_713_Two_Bad_Neighbors.html

This one is fantastic. Probably my favourite one ever.

At first I was going to just say that seasons 5-7 were pinnacle of the show and most episodes from that time are brilliant, but I think Cape Feare steals the show.

"Hey, kids! Want to drive through that cactus patch?"
"Yes" "Yes" "No"
"Two against one"

Close behind are "Lisa on Ice", Treehouse Terror with Shining, "Marge vs. the Monorail" or "Mr. Plow" and some more I can't rememebr right now.