Side scroller with depth? (TMNT, Double Dragon)

Hello, I am relatively new to Unity. I have been working through tutorials, with Playmaker FSM's, etc to learn. I am looking at making a side-scroller platform type game, but possibly with a bit of z- depth and perspective. I am not sure if the best approach is to model it all in 3D or if I can use something like 2D toolkit, but still allow a character to walk back into the depth of the scene a bit like in the TMNT arcade game or Double Dragon.

Any help is appreciated. I realize that there will be a difference when working with sprite animation versus modeling. Both interest me, but again it is the depth that I am trying to figure out so that I start with the correct framework.

Thanks.

 

Both methods are valid. You'll need to decide whether you're doing 2D or 3D. That's more an art decision than a programming one. From that, you'll know which way to go with the programming.