LittleBigPlanet is a 2D side scroller with a level editor built in.
Pro Varying level of challenge
Depending on if the player wants to breeze through the game or play as a completionist changes how difficult the game can be. LBP is pretty easy to breeze through if one is not worried about getting a perfect in each level, but for those that do the difficulty is greatly ramped up.
Con Building levels is complicated
While there are 67 tutorials to help in this area, they do not cover some of the cooler things that can be done, which means the player will be left guessing or searching out online tutorials. This also means that there is a high learning curve to creation, which is going to hold a lot of people back from experimenting with it.