@Aldrich:
Was Gol D Roger really the Pirate King??
Is Mihawk really the strongest swordsman in teh world??
Are the Admirals really the greatest powers of the World Government??
etc etc
Well, unlike all those guys, Whitebeard seems sick. That's kind of an X-factor in his strength, there's a possibilty that he'll have to "retire" soon. Or, his sickness is just a red herring for when he really fights. Questioning this title is at least understandable.
Depending on how the story goes, he may not even fight. Or, his sickness with kill him in whichever fight he gets in, kind of like Shishio vs. Kenshin.
So yeah….Whitebeard will suddenly burst into flames.:blink: