On the surface the game is fine, but when you delve deeper into actually completing the game, it becomes a nightmare!
Controls: A bit loose and at times hard to make precises jumps, but it's never enough of a major issue.
Storyline: Typical Sonic storyline, Robotnik BAD, go beat him up!
Difficulty: Murderous! It doesn't matter what difficulty you put the game on, Easy or Normal, it's hard either way and it shows that Sonic Team wasn't thinking about the players when they made the game.
Gameplay: If you don't consider getting the Chaos Emeralds, it's decent though at times annoying but you WILL fall off and die in many pits and see the Game Over screen many times before you get anywhere near the end of the game.
In one way, this is really just a 2D version of the level design in Sonic Heroes and Shadow the Hedgehog as later levels are fraught with pits and you'll fall into them for reasons not your fault and you'll have to use Trial and Error to complete them. All the boss battles happen while your running and the later bosses, especially the last one, will drive you nuts. If you consider getting the Emeralds, it will drive you absolutely INSANE! The process you have to go through is horribly convoluted. In the entirety of the large Acts of each stage you have to find 7 Special Rings. In the process of finding them all, you have to get to the end the act without dying. After getting to the end without dying THEN you have to do the special stage to get a Chaos Emerald. The levels get harder and your more likely to die as it goes on so it's not fun, especially the final acts of the game. You'd have a better chance beating Sephiroth in Kingdom Hearts 1 than get all the Emeralds in this game. Sonic Team didn't even have the courtesy of giving you a Special Ring detector of any sort to relieve the problem.
It's mainly because of the hunt for the Chaos Emeralds that I give this game a low score. In most main stream sonic games, if you do not get all the emeralds, you don't get to see the true ending to the game so whenever I play a sonic game I don't consider my game finished till I've gotten them, I don't see them as an "option". Some people consider any ending in which you see the credits as meaning you beat the game, but not completed it and I don't agree. Avoid this game at all costs if not being able to get the emeralds is going to drive you nuts and try to live with the fact that there are people in the world who are obsessive compulsive enough with sonic and/or games in general that they will trudge through this to get all the emeralds. For me, this game shows how little Sonic Team cares for it's fans and players of their games in general and how much they rely on the name Sonic the Hedgehog to sell their games. If this game was made as the first Sonic game instead of Sonic 1 for genesis, this would have been an instant kill to the start of the franchise. Sonic Team now obviously relies on nothing more than nostalgia and ignorance to keep people coming back for more.