I have given this one lots of thought, actually it was kinda obvious to me, but my favorite and in my opinion the best Simpsons season is:
Season 5What else to I have to say either than:
(1) Burns' Heir
(2) Treehouse of Horror IV - Homer and doughnut / Bart and the gremlin / Mr. Burns the dracula --- classic treehouse of horror and probably the best one
(3) Secrets of Successfull Marriage
(4) Lisa vs. malibu Stacey
(5) $pringfield
(6) Homer the vigilante
(7) Deep Space Homer
(

Lady bouvier's Lover
(9) Homer goes to college
(10) Bart gets Famous
(11) Homer loves Flanders
(12) Sweet Seymour Skinner's Badasssss Song
(13) Cape Feare
(14) Bart Gets an Elephant
(15) Homer and Apu
(16) Rosebud
***What else do I have to say I've never seen a season with better episodes***
Right behind Season 5 in my opinion:
Season 6
Season 7
Season 4
Season 14
Season 2
Season 8