I hate it!
Sonic 2 on Megadrive is a game with moments that range from "OK" to "painfully bad". The levels are too easy - they're just fast and require no real skill. If you can do Sonic 1 you will breeze through the levels in a matter of minutes without losing a single life. However, the boss battles against Robotnik are so frustrating. They require no skill and are the type of levels that you either do it the first time or spend ages and lose all your lives. When you complete them, you don't think "wow, that was really hard, I did well" you instead think "thank god I got lucky and its over now". Makes the game unbalanced and random.
OK, it has its moments, its extremely fast for a start and it has some stunning levels that look 10x better than Sonic 1. But there are too many downsides.
People criticise 3D-sonic - well, here I am criticising a 2D-sonic game. The other 2D-sonic's are great, just not this.