It's just 3 games, and 1 of them was going to be an exclusive anyways because it's half Mario.
Besides Sonic Generations was 3D Ready on the PS3 & 360 & 3DS (which is different from the none-3DS versions).
Sega always makes their games 3D capable like Warner Bros.
Where you going to play the other 2 Sonic games on a 3D TV in 3D?
Because the PS3 & 360 & PS4 & infinite & Wii U versions of the game would be made 3D ready, it's Sega.