This is the best Sonic game in a long time. It was way overdue, but the Blue Blur is finally back where he should be.
A tribute to past Sonic games and past levels is a perfect way to celebrate Sonic's 20th anniversary. The greatest thing about this is that the fans actually had a say in what levels were going to be in the game. The levels are beautifully designed, and the detail is second to none. You get to play as Classic Sonic and Modern Sonic, and tackle levels in both 2D and 3D perspectives. One of the best things about this game is that you're able to select different music tracks to play through each stage. The music is catchy, and the remixes are all great, except for Planet Wisp. The presentation is absolutely breathtaking. Did I mention how beautiful the levels are? In order to unlock bosses from previous games, you have several missions to complete in order to obtain boss keys. The boss keys unlock portals to bosses (naturally) from previous Sonic games.
I'm guessing due to how poorly Sonic '06 was with all the unnecessarily playable characters (among other things), Sonic Team has gotten extremely conservative and has gone back to having the player only play as Sonic. Listen guys, we all enjoy playing as Knuckles, Tails, and Shadow. You just have to get their gameplay styles right. Look back to the Sonic Adventure series. Just please, no treasure hunting missions. Bring them into the next game after Sonic 4 is completed (if they complete it).
The final boss in this game is also very forgettable. The story is just extremely short. But, the solid gameplay and awesome remixes of past music more than make up for it. This game is a must have, for both old Sonic fans, and those just getting introduced in the series.