Suns, remember when on the CBS bracket app you could select the team you like the most and the team you hate the most? On that page (if you click on the "team" tab) it'll list the teams by conference with the number of people that selected that team as their favourite. You can also click on "Rankings" to have the teams ranked in terms of the "most liked" and "most hated"
It's obviously not complete and a factual indicator of a team's fanbase, but it's reasonably accurate. Granted, I only have 5-6 of my friends as Uconn fans, when I can name hundreds, so it's obviously not to scale, but I'd imagine that the ranks would still be about the same.