You cant possibly think that Floyd can beat a prime Hearns, Leonard, Trinidad, Robinson, Benitez, etc. This is a guy who wouldn't even fight Paul Williams.
What's wrong with Williams? Thats a nice W. Mayweather can beat Benitez, SRL, Duran, Robinson. Why not? Hearns ruins him though.
Hagler is the one that I think would give Mayweather real problems. Great conditioning and inside fighting. Leonard might be able to win against him as well.