Charon and Fawkes were my favorite characters in the games, but their stories were a double edged sword. One hand, you could create a back-story for them yourself, but on the other, you never really knew the truth. Except cut content shows Fawkes was a security guard named Shelton Delacroix that knew too much.
I think I like the fact that they come from mysterious backgrounds. Then again, the companions in New Vegas had really well-written background stories that actually made me care. I was really struck when Boone finally opened up about his past. Or when Raul gave me insights to his long life in increments.
The little details about the companions in New Vegas were something I really liked. Like the fact that Arcade Gannon is gay. And it's awesome because he doesn't just flat out tell you that he's gay and he doesn't come off as a stereotype. His character was especially realistic in that regard.
Yeah, this time around they built characters meant to be loved and gave them enough difference to fit different kinds of people. Lily who struggles to remain a sweet old grandmother and Veronica's voice of reason being ignored. But I think everybody loved one guy in particular. Boone.
We know he was a soldier and that he's in hell on Earth. But we don't know where he came from or what he's really thinking most of the time, so he's a lot like Charon and Fawkes in that regard, making him the best of both games.