There are multiple reasons the movie's title is "Badfellas"
1. Not shooting Henry (Goodfellas) was good. But shooting Ray (Badfellas) was bad.
2. It's a parody so the name is the opposite of Goodfellas.
The Character Ray is based off of Ray Liotta who played Henry in (Goodfellas). It is also based off that character. As for the rest of the cast.