Pac and Floyd are past their peaks and on the decline, plus they've not been fighting the best competition out there.
Since 2009 Andre Ward has been on a tear, he's beaten Edison Miranda, Mikkel Kessler, Allan Green, Sakio Bika, Arthur Abraham, Carl Froch and now Chad Dawson.
Throughout that tear he barely lost a round and has dominated in those fights.
I really don't see how you can't call Ward the best boxer on the planet at the moment, he's outstanding in every area and fights the best out there.
Only Martinez or Donaire come close but their records can't really hold up against Ward's.
I see Andre Ward remaining at the top for a long time, there's nobody close to his weight that can defeat him IMO.