Well, you'd always have to watch at least two, right? Unless we're talking about shadowboxing or some creepier stalker kind of thing. :think
For the rest of my life, having already seen what I have? Greb. If I were to recommend a boxer to someone who has never seen any boxing and will only be able to watch that boxer? Undecided between Hearns, Holyfield, and Ray Leonard (yes, in that order from first to third).