I'm not saying someone in particular is better than him, I'm saying this general acceptance of him being our best defender is very definitely a new thing. Keane and Godfrey were the ones everyone had up for POTY last year, Holgate was the one everyone rated the year before, even Zouma was often seen as better than Mina. Suddenly this year it's as if it's beyond any doubt that he's our best centre half, despite him hardly ever actually managing to complete a game. He's gone past Keane and Godfrey by virtue of them looking worse, not by him looking better.
In theory he's easily our best centre half. His attributes are better than the others, I think most people would agree with that, and when he's at his very very best he looks great. By the same token though, Gomes is theoretically our best midfielder by a country mile and his best is way way way better than any of the others can do, and yet neither of them actually produce that very very best level with any sort of regularity, even when they're not injured.