The best ability is availability... If that weren't true, then Bell would top everyone's list without question. Wouldn't be debatable.
Available is thee #1 most important thing, so Bell gets dinged for that. Need to see a bigger sample size from Zeke and Johnson though, hate to draw conclusions from one full season of starting. I will say this, we've heard folks give the Cowboys OL the credit for Zeke success, following that line of logic then I'd have to say Bell played behind a much better OL then Johnson did, so perhaps Johnson season was actually more impressive? He and Fitz were pretty much the entire offense on a team struggling offensively.
Looking forward to seeing on these RBs do this year. I'd be very happy with any of them on the Seahawks.