In terms of legacy this is hard but this is my order.

Roy was simply the best and beat Hopkins easily. What he is doing now does not harm his legacy everyone knows he is past his best.
Floyd for multiple weight champion
Hopkins for his longevity
Manny when he went through the divisions and smashed everyone – short sweet and spectacular.

Side note: Floyd beat Hatton at welterweight. This was a weight that Ricky was not world class and struggled at, his best weight was light welterweight and Manny smashed him.