One of the things I always liked about Luthor is that, while he's obsessed with beating Superman and will go to virtually any lengths to achieve that goal, he DOES have moral limits and human moments. I remember particularly one story where he's hiding out from Superboy in the past, as it happens, on the exact same day that Abraham Lincoln is assassinated. Upon realizing this, Superboy resolves to try and stop the assassination, but before he does, Luthor traps him in a freeze-ray. Naturally, this is classic 'got you where I've always wanted you!' territory, and he spends hours taunting the captive Kryptonian and laughing his ass off at his enemy's predicament - but then, just as he's about to zap Superboy into oblivion once and for all, he notices what date it is - and realizes just why Supes wanted to get away so badly. Aghast and guilt-stricken that he's effectively responsible for Lincoln's death, Luthor passes up the chance to finish off his nemesis, and flees into the future, filled with remorse. The rest of the story isn't that great, but that one moment stayed with me - and that same Luthor is the one shedding a manly tear at Einstein's memorial. THIS Luthor is clearly a bit more human than the current version.