Seasons 4, 5 and 6 were my favorites. Individual episodes (that I can think of now):
-Homie the Clown
-Lisa's Rival
-Lisa on Ice
-Moaning Lisa (from Season 2; because I know what it's like to feel that way and feel like no one understands)
-Mr. Plow
-Treehouse of Horror V (I also like the later-season installment featuring "HOMER3"--that is, "cubed")
-And Maggie Makes Three
-Lisa's First Word
-Kamp Krusty
-Marge vs. the Monorail
-Homer Badman (and yes, I have slowed the ending credits )
-Homer Goes to College
Don't really have any I particularly disliked.
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The existence of the leader who is wise
is barely known to those he leads.
He acts without unnecessary speech,
so that the people say,
'It happened of its own accord.' -Tao Te Ching, Verse 17