4. Sonic CD
With the CD add-on for the Genesis, Sonic obviously had to be the mascot once more to push a new piece of hardware. With a memorable opening scene and some new ideas, some devout fans even go far as to say that Sonic CD is their favourite 2D Sonic game! The time travelling mechanic is what separates this from every other Sonic game in the franchise, and allows you visit both past, present, and good/bad future versions of each stage.
3. Sonic The Hedgehog 2
Sonic The Hedgehog 2 will be the favourite 2D title for most Sonic fans. Whilst the original Sonic suffered from a few problems like how to build and maintain momentum, Sonic 2 managed to solve these issues as up the ante everywhere else at the same time in terms of graphics, music and stage design. For most people, Sonic 2 is where the perfect 2D Sonic experience lies.