Following Sir Patrick Stewart’s iconic run, James McAvoy took over the role of Charles Xavier, alias Professor X, the leader and subsтιтute patriarch of the X-Men. He first played the superhero in X-Men: First Class, then reprised his role in X-Men: Days of Future Past, X-Men: Apocalypse, and X-Men: Dark Phoenix.

Speaking at a New York Comic Con panel, McAvoy opened up about his relationship with the films, noting that he goes “back and forth” on which is his favorite. “There’s a toss-up between First Class and Days of Future Past,” the actor explained. “I feel First Class sort of tried to do something quite different and do a different kind of tonal approach, if you like, which I thought was really cool.“

He contrasted this with Days of Future Past, which “went more sort of classic” by adapting a fan-favorite comic storyline. McAvoy continued by talking about the film’s legacy:

I don’t know—correct me if I’m wrong, I’m not trying to claim anything because I didn’t direct it or write it—but it was one of the first that did all that timeline stuff and different universe, kind of crossover stuff that we kind of weren’t used to as much back then. You know, back then, before the war, that was when we were on rations. And, you know, a can of beef was a luxury. It just felt a bit different, new.

He went on to praise the writing of the film and defended the superhero genre. McAvoy explained: “People go like, ‘Oh, you must, you know, get so bored in those big movies and whatever.’ I’m like, ‘playing Charles in Day of Future Past was, like, a proper, solid acting workout.’“

While both First Class and Days of Future Past were great X-Men films in their own right, McAvoy is correct to note that the scale of the latter was fairly novel. First Class was a prequel and soft reboot that replaced the cast of the original X-Men films in order to show the group’s formation.

Days of Future Past doubled down on that by featuring both casts and sending Hugh Jackman’s Wolverine back in time to prevent a mutant genocide. Released in 2014, this movie came out during the early stages of the Marvel Cinematic Universe. The Avengers already proved that film superhero crossovers were possible, but Days of Future Past expanded on that by featuring different generations of heroes in a high-concept time travel storyline.

What’s most notable here is that the X-Men franchise explored alternate timelines and the return of legacy cast members years before the MCU tackled either. It’s now commonplace to see actors reprise past superhero or villain roles, with Spider-Man: No Way Home and ᴅᴇᴀᴅpool & Wolverine being built on the idea.

Likewise, Avengers: Doomsday will feature the return of many original X-Men actors, including Stewart. With that in mind, McAvoy has a point—Days of Future Past was ahead of the trend.