Why do you have such a stigma about jaws purely because your own jaw is about the same size as a grain of rice? You may be jealous of Roy's normal-sized jaw, but that can never change that 1996-2003 he was an immense fighter, a far far better fighter than Moorer was at 175.
Charles was before my time and Tunney is so far back it's scarcely the same sport. I usually begin my comparisons from the Joe Louis era as there are at least some decent videotapes from then. I followed all of Spinks career and saw most of his fights. I also saw many of Foster's , as they happened. I'm not saying Roy is a greater light-heavy, as the term greater is open to lots of possible meanings. But head to head, I would bet the farm that Roy would not only beat, but possibly embarrass both Spinks and Foster. Roy had no 'jaw' problems prior to 2003. And I can't think of any fighter at 168 who would trouble him. I don't really care what he did there or how long he stayed there. That's a different discussion. If Joe Blow only ever ran in two 100-m sprints, and came in under 9 seconds both times, I'd pick him to beat any sprinter in history. Roy did not just win at that weight, he completely dominated, rarely losing a round.