Which Sonic game? The first one is quite bad, but S3&K is probably my favourite platformer ever.

Regarding my comment about the difficulty, for me it is mostly a result of the bad controls, which to be honest is a problem that plagues many games of that era. You have enemies popping out from the edge of the screen and you need to react in a fraction of a second, but the controls don't let you do so, so you need to memorize the whole game and react in advance. It is not fun for me.