I love Castle of Illusion and Quackshot a whole bunch, although I think I prefer the latter for it's ambition.
Is it just me who feels a little queasy when Mickey hits his head on a ceiling mid jump in Castle of Illusion and it goes 'THOK'? I feel sympathy pain in my skull
Most people think Castle on the Mega Drive is the strongest of the Illusion series, but I say you need to give all 5 old-school games a play - That's Castle of Illusion and World of Illusion on Mega Drive and Castle of Illusion, Land of Illusion and Legend of Illusion on Master System/Game Gear. Castle of Illusion on 8 bit is a different game to it's 16 bit incarnation, but still great.
I've not played the 3D reboot of Castle of Illusion yet, but I've heard good stuff. I've heard less good stuff about Epic Mickey: Power of Illusion for 3DS though, which is kind of a tribute to the old school games.
Mickey isn't the only one with some interesting 8-bit games by Sega either - Donald Duck has 2 SMS/GG games too - The Lucky Dime Caper and Deep Duck Trouble. For my money they're not as good as the 8 bit Mickey games, but they're still decent fun.
If you want to finished up the 8-bit Sega licensed platformer set, please do check out Asterix or Asterix and the Secret Mission for Master System if you can - they're simple games but they're solid fun too!