6. Sonic & Knuckles
Sonic The Hedgehog 3 was a great step forward for the franchise in 2D, but Sonic & Knuckles allowed players to not only play the story in this expansion but also go back and re-visit Sonic The Hedgehog 2 and 3 and play again as Knuckles. As well as providing a new game, it also provided the means of playing previous games with a new character. Bargain!
5. Sonic Adventure
Sonic’s first serious foray into the 3D world came in the form of Sonic Adventure. It was sloppy, buggy, rough at the edges, and had terrible B-Movie dialogue, but somehow the entire unpolished mess came together to create something special. Whether it was your love for the characters and the franchise over the years that kept you going until the end or some other reason, there was something about Sonic Adventure kept you playing and coming back for more, despite its hiccups.