Where many recent superhero movies have risked overstaying their welcome, “Fantastic Four, ” at 100 minutes, actually feels a tad rushed at the end, with a hasty climax that nevertheless produces some solid moments — at least a few of which, given the slow pace initially, probably should have come at least a half-hour sooner. Instead, filmgoers are treated to a lot of science, with the central characters gazing intently into computer screens.
