While I liked most of what Millar did in his Ultimate X-Men, his The Ultimates was even better, and ultimately, his X-Men run was at least partially inspired by the Singer X1. The MCU was very wise to follow a lot of what Millar did in The Ultimates, as I thought that was the best the Avengers ever were(at least I and II), but Ultimate X-Men pales in comparison to Claremont's run. And honestly, other than a tiny bit of Wolverine and Magneto's arc, the Fox-Men films barely touched Claremont canon. If the MCU looked at that run more faithfully, the general audience would still be looking at fresh content.