If you're going by resume he's #2. The only other option is Bisping.
Weidman has looked very good, but he's only beaten Maia (if we're talking about over-rated I'd start with him) and Munoz.
Belcher is more deserving of a title shot than anyone Anderson has ever faced as champion other than Henderson and Marquardt. Finishes over Palhares, Cote, and Gouveia and his most recent loss was controversial as hell (although I scored it for Akiyama myself, barely).
Bisping has more wins, but tends to win by decision and has some losses mixed in that were much more clear cut than Belcher's loss to the sexy one.
Weidman's only wins are Maia, the guy who submitted Chael Sonnen regarded by everyone as the number two middleweight in the world and Munoz but Belcher's higher than him because he beat up Gouveia who isn't even in the UFC anymore, hasn't been for years, Palhares who doesn't have a single win over an active UFC Middleweight and no top ten fighters ever and Patrick Cote whose only win in the UFC in four years is a controversial DQ over Alessio Sakara...
Just stop, seriously.