As a post-apocalyptic teen-centered story, this series falls short of the Hunger Games. There are certain similarities; however, in this case, when the kids are thrown in an "arena," they work together rather than try to kill each other. The added element of amnesia allows for more suspense and a few interesting twists in the first film (one of the reasons I think I like it better), but this idea is then mostly dropped from second two movies, missing the chance to explore the theme of building identity and self. Overall, theme development and in depth characterization is often dropped for the sake of dramatic moments.
I was also surprised to see this series devolve into another zombie story. It was almost as though the story decided to mash together as many horrific things as it could: An unstoppable disease that turns people into zombies, a series of solar flares that destroy the environment and billions of people (oh, and that somehow caused the zombie disease), losing one's memory (for no fully disclosed reason), mad scientists who torture children for the benefit of the wealthy, and mutant spider-robots (because, why not?). It also seemed to kill off characters just for the sake of killing them off like it was a George R.R. Martin rip-off but with less reasoning behind it.
I did notice a resonating image from the last movie where two of the main characters are walking through a city in which everyone is wearing masks (except them, of course). Considering the movie came out about two years ago, it seemed eerily prescient (although the boys pointed out that the people weren't social distancing). It was also interesting that the bad guys were the ones continually walling out the less fortunate, but were spreading the disease amongst themselves anyway.
I still appreciate the production and performances in the movies. While there are plot holes large enough to fly one of their massive helicopters through, if you can suspend your disbelief long enough, these are still popcorn-worthy films. However, unlike the Hunger Games, I don't have a strong desire to see these again.