Great game, but it's WAY too hard!
There's just one problem with this game - the difficulty. The first two acts of the stages are ok. But when you get to the third one, you have no rings to protect you. And before you even get to the boss in the third act, you have to make your way around spikes and bottomless pits which you sometimes can't see. And since you have no rings, you may end up dying before you even get to the boss.
Now the bosses are pretty hard. Like I said, you have no rings to protect you, so you can't afford to get hit even once. In the first boss battle, you have to jump over black balls that bounce towards you. Some of them bounce higher than others, and since the Game Gear's screen is quite small, you'll have very little time to react.
You can get through the game without collecting all of the Chaos emeralds, but in order to save Tails, you need all the emeralds. They're somewhere in the second act of a stage, but finding them can be quite difficult, as they are well hidden, and when you get through most of the stage, you may have already missed it and can't go back to look for it.
Having said all that, this game is still a lot of fun, even if you can't get past the first boss. It's not impossible to complete the game, you just need some patience and after playing it for a while, it won't be as difficult as it seems.