Honest answeres only, with reasoning. http://www.youtube.com/watch?v=v9FmVXjfefs&mode=related&search=
I'm at work and can't watch the youtube highlights, but I can't call it since I've seen so little of Robinson @ 147. The only footage I've seen of SRR @ 147 is short and grainy. I've seen more of him @ 160 where he was still a hell of a fighter but he was more vulernable (and that was even before his dancing career).
Check it when you get home, it has two parts. Just one of many great tribute videos to SRR. I know that his best years were not filmed, which makes this footage all the more scary to me.
Since he was probably even greater at Welterweight than Middleweight (seeing as how he was fighting as a Welterweight against heavier guys), he would probably have been unbeatable - or as much as that is possible.
I won't come out and say I favor any WWs over him, he was like a mini-Calzaghe in that divison, way ahead of his time. Though there are surely some fighters who have a very decent chance against him.