Really the only thing I remember about the first one is that after the movie was done, I realized I was on the edge of my seat basically all movie. It might be dumb, but it succeeds as an action movie.
First just felt the most realistic to me (probably because it had a lot of military scenes and was probably a Pentagon propaganda) and a lot of the interactions between the humans just made sense to me.
2 wasn't that bad imo because I only watched it for cool robot fights and a lot of the scenes were still memorable. Next ones get progressive worse, literally the only thing I remember is that they had Sentinel Prime, robot dinos, and robot knights. Felt like cash grabs