Luthor never became godlike, he always screws it up before he can enjoy real powers because he is a retard.
Doom hasn't been a singleminded nemesis to Richards for decades now. His plans are always more grand than that.
Lex was president and fucked that up, again, and got his ass kicked and exposed like the prick he is. Doom is loved in Latveria and even when he became leader of the world he was still loved.
Doom never plays the good guy, even if it suits him. He helps when it's in common will, but he doesn't pretend, he doesn't act. That's beneath him.
Doom fought Gods but what differs him from Lex is that he won.
Doom is a sorcerer as much as he is a science genius. He fights demons and wizards and knows how to use magic. Lex only knows how to use kryptonite for everything.
Doom is not a villain and is no lunatic. He wants power but once he has them he'll fight for the earth and crush any actual villains. Lex had that chance but always comes back to being a retard that hates superheroes and ruins everything by picking fights with them.
Doom is so far from Lex that they can't even be compared. Lex is manlet with an endless inferiority complex.