No way would Christopher have been anything if it wasn't for Tony. He was too reckless in the early seasons, and too much of a junkie in the later ones. I don't know if he would have been clipped along with Brendan (although it would be likely given that Tony basically saved his bacon from that situation; if he wasn't related would Tony have done that?), but he probably wouldn't have been given as many opportunities to get ahead.

There's a chance he might have become a made guy, but even if he did he would have never amounted to more than that.