Here comes the nightly Banjo v Steve argument but here's my take.
Both deserve to be in but for very different reasons. Banjo is what some would consider a Lost Nintendo Character, A character who at a time was right there alongside Mario, Link, Pikachu, and Yoshi. Banjo was a huge part of the N64 era and was kind of a Nintendo character and he should be reunited with his Nintendo brethren. Plus Banjo is super popular which for that he should be in.
Banjo should be in for 1) His Connection with Nintendo and 2) because he is a Fan-Favorite.
Steve deserves to be in cause he's from one of the biggest Gaming sensations since Tetris which is Minecraft. Minecraft is the biggest indie game of all time and one of the best selling games of all time for that matter and has influenced gaming as a whole. Minecraft is huge in this day and age of Gaming so of course it deserves representation in some way. Minecraft is Iconic. Everybody who's Anybody knows what Minecraft is and it's such a sensation that it's likely not going anywhere in a long, long time.
Steve should be in cause 1) Minecraft is Iconic 2) Minecraft is one the best selling games of all time and 3) Minecraft is the biggest Indie of all time and there's no better way to represent indies than Minecraft in Smash.