I thought the first half was about as great and as perfect as could possibly be. Like, holy-crap-they-finally-nailed-the-Fantastic-Four, well-on-its-way-to-top-ten-MCU territory for me.
But after the big (and admittedly incredible) space sequence, once Franklin was born, and Reed gave that weird, way-too-honest press conference, I thought the second half (or however much was left) was a significant step down. Not bad, necessarily, but average at best and rushed as hell.
In fact, it's pretty obvious there was a good 20 minutes worth of material, at least, cut from the movie throughout. And maybe it was all terrible/rightfully cut, but it still needed another 20 minutes or so of… something, I don't know what. More character development? Reed not being such a damn mope all the time?
All I know is that Galactus was the one thing that was outright terrible, IMO. He made absolutely no sense to me, and neither did the final plot to take him down.
As mentioned earlier, for such an apparent big, bad, planet-consuming god I was shocked at how small he was (relatively speaking), and how easily beatable he seemed. He had no interesting or world-dominating powers, and I feel like Godzilla, for instance, could have mopped the floor with him. Glactus seemed so beatable that it made no sense whatsoever why the military - or literally anyone else - wasn't working in tandem with/alongside the Fantastic Four. I mean, movie-wise, I get it. The Fantastic Four vs Galactus - in the simplest/cleanest way possible - was clearly a purposeful choice, in the spirit of the comics, etc. But from a more realistic, live-action perspective, I just couldn't get over how dumb it was that all of Earth left their fate in the hands of four people, one of whom just had a baby. Like, fifteen fighter jets barraging Galactus with missiles seems like it would have easily done the trick. Or hell, just luring him to the desert and then nuking him. But no, let's leave it up to four people and their flying car smack dab in the middle of the city.
Trust me, I understand how much we were already suspending our disbelief up to that point, but man that really bugged me. It just felt so half-assed and ill-conceived. Never mind not even bothering to show how a guy the size of a building consumed entire planets or why (other than his "eternal hunger" or whatever). Put bluntly, it was one of those instances where slavish devotion to canon - i.e. to some ridiculous idea a couple of guys randomly had one day in the 1960s, probably after smoking a joint - hurts a movie rather than improves it.
Anyway, it was a fun, then very-okay time at the movies, but I doubt I ever watch it again. And this is coming from someone who really, truly wanted to love it.