Which 2d sidescrollers on the rise. Would it draw more interest with a 2d game rather than a 3d one?

Yes, but if the 3d effects can be in the background, they can't be behind it actually (because 3d is rendered on the background 0)Also you can make a 2D game (gameplaywise) and still have 3D effects going on in the background.
Like Donkey Kong Wii or the later Legendary Starfy games.
