Edit: (Part of this is in response to the "either they're the best or they're not" thing you edited)
The way I always see the "arguable" qualifier used, is when they're in the discussion for the best. That's using the definition of the word. I thought it was used commonly enough that nobody really had a tough time interpretting it. I've certainly never seen it used in hyperbolic examples like yours. I would say the Wizards, Hawks, Mavs, Grizzlies, and Bulls are all in the argument for best big rotation, actually I've already said that... I would say there's too many variables for one definitive answer, just like if you were going to argue about the best scorer.
If Nene is going to continue to struggle with this injury the discussion will change. But he was healthy in the playoffs last year, and Nene/Gortat dominated Boozer/Noah to beat Chicago. Wizards have added even more playoff experience to their core in Pierce and they're playing better than last year, even with Nene less than 100%.
Also, I have no problem with criticism, or even not nice criticism, I just feel that when you receive it you at least deserve to know why.