X-Men was one of Marvel's hottest properties at one time. It isn't anymore. Ever since Marvel decided to do the MCU, they have slowly devalued the X-Men property which has pissed off Fox. They don't do X-Men toy movie tie-in toy lines. You don't see that much X-Men merchandising anymore. In the comics, the X-Men are mostly isolated from the rest of the Marvel Universe. Their hope is that Fox will eventually give up on X-Men but with the recent success of Deadpool, I don't see that happening. But I do think the X-Men movies will continue to make less and less money.
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