Superman is smarter but was raised on a farm in Kansas and has had little exposure to thinking on a tacticle and strategic level.
Actually, he's a classically educated journalist trained to view a situation from any number of perspectives.
Wonder Woman is a warrior and thinks like one first without reguard for the consequences.
I hate how current DC gets that wrong. WW is a warrior, but she's more than that. She's not even a warrior first. She's a princess, an ambassador, someone who resorts to violence only when all other means failed, and her main weapon is not a sword (although you could get this idea from current DC), but a lasso, a non-lethal weapon. Anyone remember how big a thing it was when WW killed Maxwell Lord?! She did it because their was no real alternative (well, Superman and Batman later said there had to be, but I still don't see it, and I'm a pacifist). Before that, she didn't kill, and afterwards she still seldomly did. Only with the New 52 she's like "Look, monsters, let me cut their heads off".
Martian Manhunter is an alien and has a non human thought process.
He's also the oldest member of the League (aside from WW, if you take her immortality into account) and has been on earth since the 1950s, with plenty of time to observe humans. Another fact most people tend to forget (especially DC editorial) is that J'onn is a detective. Yes, Batman isn't the only detective among the League.
Plus, we've seen J'onn taking up organizing duties for the League several times in the past, so he definitely has tactical experience.
Flash thinks faster but is at heart a scientist and examines everything through that lens.
Green Lantern is a fighter jock who takes risks.
That's true, actually, but only for Barry Allen and Hal Jordan. John Stewart actually is an ex-marine and an architect, so he definitely knows about plans and battles.
Batman is the only one who has trained himself to think like a leader.
First, WW is the Princess of Themyscira, she's probably been trained to be a leader and therefore think like a leader.
Second, Batman didn't train himself to be a leader, he trained himself to be a detective, scientist and martial artist. The leader thing only began when Dick Grayson came along, so he started out with a teenaged boy to 'lead'.
Also, you forgot about Aquaman, you know, the character this last couple of posts was all about. He is a king, an actual king, leading the armies of Atlantis (and the occasional whale) into battle. If he ain't a leader, who is?!
Superman has super-senses and super-speed, his alter ego is a writer, ergo he's pretty much the most intelligent being on earth)
Bulls@#t, if he was that smart he wouldn't fall for the kryptonite thing every freaking time, he also would have taken Lex Luthor down by now. Seeing as he hasn't done either of those I call shenanigans on the whole super smarts thing.
Ah, yes, Kryptonite, the embodiment of lazy writing. Of course, characters can only be as smart as their writers want them to be, so if a writer is to lazy to come up with a real threat, he has Superman being caught by Kryptonite, even if it really doesn't make any sense. Of course, there have been writers who were able to use Kryptonite in an original way, like Mark Waid in "Birthright", but there's a reason Denny O'Neil once had all Kryptonite on earth turn to harmless lead. It's a lazy excuse for a threat.
As for Lex Luthor, I guess you mean corporate Luthor (as Superman has taken down mad scientist Luthor basically each and every time they confronted each other). In this case, you have to take Superman's respect for the law into account. He can only bring Luthor down with hard evidence that would hold up in a court of law, so there's not much he can do. And even with the evidence, Luthor has enough highly-paid lawyers to keep him out of prison (also seen in Waid's "Birthright").
