Well ofcourse, most group has unbalance popularity but I mean it's very obvious how Luhan take most of the fan's portion. In concert most people's will scream his name. And everyone will be talking about his look when watching their videos. Like seriously, poor Chen, people's need to give some recognition to him. Just read the youtube comment on their medley teaser, less people's mentioned Chen. He's the main vocal for god sake.
EXO M popularity imo:
Luhan >>> Kris > Lay > Tao >> Chen > Xiumin
It's not obvious on EXO K because Kai, D.O and Baekhyun almost got the same amount of fans. While, Chanyeol, Suho and Sehun still got plenty.
I wonder how long Luhan will keep his fans before they lose the interest. This is clearly not good for their overall popularity.
But for the sake of humour, i'll quote what Kurumiluff said,
"if you take all the exo fans im pretty sure the exo member with the least amount of fans still has more fans then the ukiss member with the most amount of fans " By Kurumiluff