The hedgehog's finest hour.
All the graphics have been updated and redesigned. Sonic has brightened up a bit and gotten a new shade of blue. Tails is a little more competent with his usable flying technique. And there's a save feature.
The game isn't as lengthy as 2, or at least it doesn't seem that way, but it irons out the difficulty bumps from its predecessor. Each zone is harder than the last. Also, the music is possibly at its finest in this game. Every single tune is instantly memorable.
Also, the control is still beautifully slick, but Sonic still just stops when he tries to run from the middle of a ramp. It's difficult to explain, but it's always been an issue with the series.
The finale is also suitably epic, with a trifecta of Robotnik battles. Knuckles is introduced as a villain (that'll change with Knuckles) and a foil to Sonic.
And in this game, there are more quick-thinking moments. In the first two, the flow was always constantly fast. In this one, there are several spots where part of a level starts falling apart or pushing inward where you have to think faster than before and get out of the jam. It works remarkably well to add challenge and excitement.
Last Words: Simply amazing. You owe it to yourself as a gamer to play it.