A brilliant follow up to the main series of Sonic, Throwback to the fans, and a spit in the face of all naysayers.
This game is a throwback for the main fans who couldn't get enough of sending Sonic blazing across the levels collecting rings and chaos emeralds along the way to break down Dr. Eggman (Robotnik for hardcore fans) 's evil ideas. This game picks up immediately after Sonic 3 & Knuckles but it features Sonic alone facing against Dr. Eggman (Sorry Tails and Knuckles Fans).
Sonic retains all of his basic gameplay but for all the Sonic Adventure fans Sega included Sonic's homing attack as an essential move to get across pitfalls and in some manner keeping the game moving at a fast pace. It plays very much like the classic games in terms of you have to use fast movements in order to refrain from getting killed by slipping off cliffs and falling on spikes. You have hazards though alot more then what was seen in adventure or sonic unleashed but then again they occured in classic sonic games so no negative feedback.
The game's graphics are beautiful and dont tear or shift to a lower resolution while Sonic is moving. Don't expect any voice acting to take place in this when this game was made there isn't much more then the sounds of sonic running,jumping, dashing, or springing into the air which is heavenly to those who played the Blue Blur back in 1991. The music in the game is reminiscent of Sonic 3 but its a little more corny then it needs to be but you won't care cause you'll be busy speeding and trying to get all the rings you can.
The Level design is wonderful especially the first level Splash Zone which looks identical to Green Valley From Sonic 1 and each level has 3 acts in it with the fourth being a battle against Dr.Eggman. In each of the levels there are some tedious activities (usually the 2nd or 3rd Act) you'll have to do to complete the level but then again Sega wants to challenge you especially those who just want to say something bad about a Sonic game.
They brought back the Chaos Emerald Levels which like Sonic 1 you have to get Sonic through a maze to acquire the chaos emeralds however unlike Sonic 1 there's a time limit and instead of controlling Sonic in the Special Stage you control the maze and have to lead him through the corridors this is about the most tedious thing in the game. I found it irritating but it was a good irritating (Don't ask just roll with it).
The Difficulty factor varies among people who play Sonic games so we'll skip this part but for me it was just right, I'd say try it yourself.
However while the game is great as a throwback it isn't without its share of problems. For one, the game's length even though its episodic is a bit short and you can select whichever level you want to play which is fine but it kinda cheapens the deal and doesn't surprise you like old Sonic games did. Some complaints are that the physics of the game seem to be a little off, in certain areas they are but not enough to stop game value since Sonic is all about Speed and the Speed is back, people ! The music got on my nerves sometime but then again when you're in play the music just fades away and all you're thinking about is breaking Eggman's toys and speeding through another level.
So as a final verdict I say give Sonic 4 a shot, its a good game not so long but then again they have Episode II coming out and I hope it features more levels then Episode 1 and if you collect all of the Emeralds then you get a sneak peek at what Episode 2 is all about but I wont tell.