Welp, the FoX-Men movies sidelined the fuck out of Jean, Storm and Rogue (and Cyclops!) and went all about Magento, Charles and Wolverine so... of course those were the three that saw their popularity expanding. But the former three (and Cyclops) are some of the most popular Marvel comics characters for sure, at least before the MCU came along and turned Iron Man and Captain America into pop culture icons.
Storm has such a rich history in the comics, it would be a disservice if she's not one of the main faces of the mutant corner of the MCU. If they do Rogue justice, she could become the next big thing for the MCU as well. I do think Jean is a little bit more complicated, since her popularity often just seems too tied to the Dark Phoenix storyline.