The only other one in recent times was Whitaker vs Chavez. The Pound For Pound debate only really became official in the 90s, although there's a few other fights you could strongly argue to be between the best 2 fighters in the world.

Leonard-Duran might well have been although I believe there were people who might have argued for Salvador Sanchez or Alexis Arguello being one of the top 2 at that point. Fighting Harada-Eder Jofre is a possibility, but it's hard to say either was acknowledged as the best fighter in the world at the time, that may be retrospect creeping in.

The only other fight that I can say you would have to say was between the best 2 fighters in the world at the time was the Hank Armstrong-Barney Ross fight, who were considered the two best, although this was before anyone really used the term Pound for Pound. A similar argument could be made for the Billy Conn-Joe Louis fight, as Conn was considered the best at that point in time with Louis certainly around the top.

But, with pound for pound being a relatively new phenomena in being ranked, it is hard to judge.