As according to the British Xbox 360 magazine Xbox World 360, the magazine tends to talk SEGA's Takashi Iizuka about 2D Gaming.
I think there are various kinds of 2D platformer and each one of them focuses on different game elements. In the case of Sonic games, I put a premium on the game tempo of the stage.
A game cannot be constructed with only speed elements and a game with only jump actions is not a Sonic. Though jump actions bring a feeling of tension and cause a lot of stress, it’s an element giving the player a great sense of achievement when completed.
In addition to that, maximizing the feeling of achievement and exhilaration in a game whilst still providing the speed is the basic concept – and also real pleasure – of Sonic games.
Many 2-D Sonic games date back to 1991 when the first Sonic game was released. However, they're still are 2D Sonic games today (mainly on the Portable Nintendo consoles, such as the Nintendo DS).