The best of the retro Sonic titles and one of the best games out there.
Sonic 3 improved on what was already a great game. The whole game is more fun than both the amazing original Sonic and good Sonic 2. It's better for little kids too because there is a save feature which will save your progress when you complete a zone.
So the story goes that Dr Robotnik has tricked the guardian of Angel Island, Knuckles, that Sonic is a bad guy. Whilst speeding across the cost of Angel Island in his super from, Sonic is ambushed by Knuckles who steals all of the Chaos Emeralds. And so the game begins.
Your player characters are Sonic and Tails. you can play as either character alone or control Sonic and have Tails follow you. A second player can control Tails if the game is played like this. Tails can be handy when he follows because he can help you pick up rings and help take out enemies. There is some slight difference between both player characters. Tails can fly which will make the game easier in several places, but Sonic has the ability to use different jump techniques when he is surrounded by different shields. For example the lightning shield will enable Sonic to do a double jump and the fire shield will enable him to do a jump dash.
Anyway there are a total of six uniquely themed zones each with two acts, which both involve running, leaping and spinning to the edge of the stage collecting as many rings as you can. There are some level specific gimmick such as snowboarding, going underwater, being shot from cannons, riding floating platforms which rise as your speed increases ect, the help separate the zones and make them all feel unique. The game is a real blast and very fun. At the end of each act there will be a boss battle. The game's difficulty is not too hard nor too easy.
In the stages you can find hidden bonus rings in nooks and crannies in the levels. Jump into them to enter the bonus stage and get a chance to earn one of the seven Chaos Emeralds. The special stages are controlled on rails (in other words - moving forward constantly) and you will have to collect all the blue spheres and avoid the red ones. This can be quite tricky sometimes as the stage gradually gets faster; controlling Sonic or Tails becomes quite hard when the speed is at it's maximum. But if you can complete the seven stages and earn all seven chaos emeralds, you're in for a treat (if you're playing as Sonic - no reward for Tails fans such as myself though)
There is also a competition mode where you can challenge a friend. You can play as either Sonic, Tails or Knuckles and race a five lap race along five short, but satisfying tracks. you can also do these tracks solo for time trial if you wish. This mode wasn't needed to give Sonic 3 a perfect 10 score, but it's a very welcome extra.
Graphically the game is very impressive for 16 bit. Sprites have a lot of colour on them and the backgrounds are vivid and detailed. The music (rumoured to have been done by Michael Jackson (RIP)) is pretty much what you'd expect from a Sonic game - Just plain awesome. This was the first Sonic game where act 2 music is remixed from act 1.
Sonic 3 in conclusion truly is a master piece and a must get for anyone. It improved on the already great Sonic the Hedgehog formula and as a result is one of the most enjoyable games of all time. It is included on the Sonic Mega Collection games and is downloadable on the current generation of consoles. I believe it is also on the "Ultimate Mega Drive (Genesis) Collection" - something like that, for Xbox 360 and PS3 I think.