The thing is if your arch-nemesis is a nigh-invulnerable godlike superfucker and your only real powers are being very rich and very smart, you'd better have some basic common sense or you're not going to seem very threatening.
...this is goddamn Superman we are talking about. If anyone in his principal cast starts showing the slightest hint of common sense, the entire premise comes crashing the fuck down.
...although on the other hand, All-Star IS the only Superman story I can think of where I've looked at Clark Kent and said "Yeah, I can see how people wouldn't know he's Superman."
All of which to say: Lex has been depicted a lot of different ways over the years; some prefer the wacky mad scientist version and some prefer the menacing businessman version. They've both been done well and they've both been done poorly. (JLU even managed to go from an awesome version of the latter to an awesome version of the former from one season to the next.) I can understand if Wacky Lex isn't somebody's cup of tea, but if we start pulling at the Suspension of Disbelief thread then the whole thing's going to unravel pretty quickly. Which is of course true of pretty much every superhero story ever, but I'd argue it's ESPECIALLY true of the one where a guy becomes unrecognizable by putting on glasses.
And that's without beginning to get into all the crazy Silver Age shit.
...anyway. Tired glasses jokes aside, I think Lex is played best when he's played as a character who claims that Superman is holding humanity back from rising to its own potential, but who deep down really just wants everyone to worship HIM instead; who has convinced himself that he'd reach his full potential if only Superman would quit thwarting him, but who actually constantly thwarts himself.
Cornell's run on Action Comics is based entirely around that premise -- it is, after all, a book where we see Lex Luthor without Superman, and he hasn't gone out and cured cancer or done any of the other great things he's always sworn he'd do if it wasn't for that meddling alien.
A point hammered home in the following exchange, from the latest issue:
Lex: Joker, please -- somewhere under all this "madness," real or assumed --
Joker: You know what? I think if I can just kill Batman, I'll save the world!
Lex: Interesting. A delusion akin to my own certainty that --
oh.
Joker: HAHAHAHA! Oh, the rich and powerful! Takes them a while to get they're being laughed at!
(Lex punches Joker in the face.)
