Yet, to me, Eisenberg seems a natural choice to play the Lex Luthor that I grew up reading about back in the early 1960s. This is how the Superman Wiki describes that Lex:
In Adventure Comics #271 in 1960 (written by Jerry Siegel), the Silver Age origin of Luthor is retroactively revealed, along with Luthor finally gaining a first name, “Lex.” It was revealed that when Luthor was a teenager, his family moved to Smallville, with Lex becoming a large fan of Superboy. In gratitude and to encourage Lex’s scientific pursuits, Superboy built for Lex a fully stocked laboratory. There, Lex began an experiment in creating an artificial new form of life, along with a cure for kryptonite poisoning.
However, when a fire caught in his lab, Superboy mistakenly used his super-breath to extinguish the flames. This rescue attempt spilled chemicals that caused Luthor to go prematurely bald and destroyed both his kryptonite cure and his artificial life form. Luthor attributed Superboy’s actions to jealousy and vowed revenge. First, he tried to show Superboy up with grandiose technological advancements to improve the life of Smallville’s residents, which time and again went dangerously out of control and required Superboy’s intervention. Unwilling to accept responsibility for these catastrophes, Lex rationalized that Superboy was out to humiliate him, and vowed to spend the rest of his life proving to the world he was Superboy’s (and later Superman’s) superior by eliminating the hero.
In other words, the young Lex was a boy scientist: a nerd! Not the thick-necked bruiser I have seen in more recent Superman cartoons and comic books, but a nerd!
Eisenberg would be perfect.