X-Men 1
Credit to the original movie for kicking things off, but if you go back and watch it again, you’ll see that it doesn’t really hold up all that well. It’s still good, but it’s also incredibly dated as hell, from the costumes to the effects to just about everything.
At the time, the movie had a way better cast than anyone could’ve expected. Ian McKellen absolutely nails it as Magneto, for sure; Hugh Jackman gives a surprising turn as Wolverine, and Patrick Stewart is doing great at playing himself. But with the exception of them, plus Mystique and debatably Rogue, no one else in the film has much to do besides stand around in 1990s fashion and show off their power for a minute or two before being shoved back into the closet. You could take out the other characters and little would change except for, thankfully, Halle Berry’s fluctuating African accent and the awful line “Do you know what happens to a toad that’s struck by lightning?” . That alone doesn’t make the original movie not good, but it definitely helps.