It's interesting. Rosenbaum's version of Lex Luthor was pretty unusual among Lex Luthors.
I've never seen the SUPERBOY series. But across Gene Hackman, John Shea, Clancy Brown, Jesse Eisenberg, Michael Rosenbaum, and that other one, the main elements of Luthor is that he is an egocentric, self-serving con artist dedicated to amassing wealth and power, who guises his confidence game in different guises.
Hackman guised his con (destroying populated areas to create real estate) in flair and costumes and not much else. He was a huckster version of Luthor.
John Shea guised his con (sabotaging federal and municipal projects so Lexcorp could 'rescue' them at a price) in an extravagant arrogance and a facade of fair play that masked a petty, bitter, vindictive, and eventually deranged personality. After Clark and the Daily Planet destroy the Luthor empire at the end of LOIS AND CLARK's first season, Luthor is reduced to a homeless madman living in a sewer with his only ambition being to marry Lois Lane even if he has to brainwash her into walking down the aisle.
Clancy Brown guised his con (technology that would defend the human race made while destroying any competition) in philanthropic futurism, a mask for how the only future Luthor cared about was his own dominance and superiority and mastery of all other life.
Jon Cryer guised his con (exploiting human racism against aliens) with a fake redemption story and extravagant charisma that eventually gives way to his only priority being his ego and his grudges.
Jesse Eisenberg guised his con (calling aliens out as threats for other heroes to destroy) in a guise of geeky, chatty analysis and humanism, but when he murders his own assistant to maneuver Batman to fight Superman, it's clear that he simply enjoys seeing people fight each other on his behalf.
Then we have Michael Rosenbaum, who noticeably played Lex instead of Luthor. Lex's character is defined for me across several scenes over the series. The first is in "Cool", where Lex tells Martha he's hosting a gathering of local farmers at the Luthor mansion to discuss investing in them. Martha and Jonathan attend and find: no other farmers are present. Lex invited only them. Lex expresses his wish to invest in the failing Kent farm so they can buy advanced farming equipment, vastly increase their harvests, for which Lex would take a profit.
Jonathan protests, saying the Kent farm is a family business that never took outside help. Lex hands Jonathan a file revealing that Hiram Kent, father to Jonathan, accepted numerous government subsidies in lean years. "Why are you so interested in our family, Lex?!" Jonathan sputters, incensed at this intrusion.
"Your son brought me back from the dead," Lex answers, sincere in his gratitude for how Clark saved Lex from a car accident and performed CPR when Lex had stopped breathing.
Lex is sincere... but note how his approach is intrusive and domineering. He lures the Kents to his home under false pretenses. He deliberately creates a situation where he has more information on them than they do on him. He establishes a position of superiority where, despite claiming he would only be an investor, his dominance is absolute. Lex is taken aback when Jonathan turns him down.
Lex doesn't know how to create a relationship of equality and trust with the Kents. He doesn't realize that, to be a friend, he should simply be present and available, rather than trying to control and maneuver them. It never occurs to him to write up his offer, send the Kents a polite letter, assure them the offer is always open, and to simply be a good buddy. He has to be in charge. But Lex can't and won't see it, and his guise of empowering investment is in fact a con -- for himself. Lex has convinced himself that he is a servant of the world when the truth is, it's simply a facade over his actual goals.
In "Lexmas", Lex declares his worldview: "What I want more than anything is to live happily ever after. And do you know what the secret to happiness is? Power. Money and power. Once you have those two things, you can secure everything else." This culminates in Lex hiring a hypnotist to engineer a breakup between Clark and Lana, followed by Lex dating Lana and engineering her alienation from all her friends, then having her injected with drugs that make her experience all the symptoms of pregnancy to induce her to marry him. Lex needs everyone in his life to be totally dependent upon him and give up all their secrets to him.
In "Descent", after killing Lionel Luthor, there is an angry confrontation between Clark and Lex. Clark accuses Lex of only caring about power and control. "This is Smallville!" Lex sputters. "Meteor freaks! Alien ships! Cryptic symbols! Someone has to protect the world!" Lex further accuses Clark, not incorrectly, of causing Jonathan Kent's death. "Why did Jonathan Kent always look so tired?" Lex says cruelly. "Was raising the perfect son really that much work?"
This is a conflation where Lex has woven lies and truth to present a self-flattering image of himself as the wronged party. But the truth is, Lex has experimented on meteor mutants to create weapons for sale and power to enrich himself. He doesn't care about protecting the world. And Lex knows that Jonathan loved Clark wholeheartedly whereas Lionel always held Lex at a distance.
We come to the endpoint of Lex's denial: he takes control of the Fortress in the Arctic and confronts Clark, declaring, "You didn't trust me with everything you had!" Lex activates a Kryptonian Orb that he believes will grant him control over Clark -- instead, it causes the Fortress to collapse with Lex inside. When we next see Lex: his body was crushed and frostbitten so badly that his face has been seared away; he's immobile in a chair; he's dependent upon cardiopulmonary bypass and a ventilator just to survive; he's using a voice synthesizer just to speak. The charisma of Michael Rosenbaum has been sheared off by ice and hate.
Lex confronts Clark and Lana and declares, "Clark Kent and Lana Lang. You've destroyed me in every possible way." Except -- it was Lex who triggered the collapse of the Fortress when Clark begged him not to and Lana wasn't even there.
Lex's self-deception is how he guises his con; he has conned himself into thinking he is the world's saviour and it's only other people who steered him to a dark path.
So, Michael Cudlitz? He's Luthor with Clancy Brown's dominating approach, with a measure of Rosenbaum's self-righteous self-deception and the attitude that nothing is ever his fault, and any fault he assigns to others must be punished. But there are none of the charismatic layers that the Cryer and Rosenbaum brought to the role, only the underlying brutality which has become the text rather the subtext.
But to be fair, this is who Lex Luthor is once you strip away the veneer of charm and intelligence. Lex is a thug.
