Looks like Donald's nephews' videogame resurrection went over so well that more revivals are coming. In the case of Castle of Illusion, as you can see, the game mechanics have been changed so it's not quite the side-scroller you remember, though the basic story's the same. (side note: why do evil villains live in such cold castles? Don't they like being comfy too?)
I remember well the ads that proclaimed "Genesis DOES! You can't do this on Nintendo..." Nowadays, obviously, we know a lot of the things you can't do on Genesis, and it's clear that Sega is taking advantage of that knowledge to DO now what they could not then.
Trailer after the jump.