I haven't seen F4 yet, but this is where I sit. I just assume those that say GL is one of the worst movies ever are young or haven't seen a ton of super hero movies. I'd say it's middle of the pack. Catwoman, Steel, Batman & Robin, Superman 3/4, pretty much every marvel movie before Singer's X men or Raimi's Spiderman are complete horse shit.
Looks like Man from uncle is finally in town, going to give it a watch tomorrow.
We have been spoiled in recent years. It's hard to argue that there were even 10 pre-2000s Marvel/DC superhero films that were better than the lower tier MCU films, or Man of Steel. Especially if we are just looking at Live action.
After the first two Superman films, the first 4 Batman films (if you are generous and count both the 1966 film and Batman Forever), and Blade, you are pretty much left with Howard the Duck tier films.