Well, I might as well add my two cents.
Let's analyze the characters first :
Captain America : adept martial artist , master strategist , vibranium shield.
Batman : master of 127 martial art styles, master tacititan, sophisticated gadgets
Superman : Excess of 100 ton strength, invulnerability, superspeed, heat vision, freeze breath, tornado breath, etc.
Thor : Excess of 100 ton strength, invulnerability, magic hammer that has complete control over the elements, teleportation with hammer, eons of fighting experience.
Wonder Woman : Excess of 100 ton strength, invulnerability, superspeed, unbreakable lasso, unbreakable silver bracelets, thousands of years of fighting experience and combat training.
Iron Man : highly sophisticated armour with repulsor blasts, missles, Mach 10 flight, etc.
Now doctorstrongbad did the predictable route: He paired the obviously compatible characters to fight each other.
Superman vs. Thor : No arguments.
Captain America vs. Batman : We'll get to this later.
Wonder Woman vs. Iron-Man : Any repulsor blasts can be deflected and dodged. Iron Man would have a hard time countering a person moving at the speed of sound and pummeling him with near-Superman level strength. Iron Man loses.
But here is my view : When Thor enters the battle. What does he say? Usually he cries out something to the effect of " THOU ART YIELD AGAINST THE GOD OF THUNDER, THOR!" Something like that. Let's see. A guy hovering around with a seemingly magic hammer and proclaiming that he is the actual god of thunder, Thor. Superman has already met his universe's Thor so he sees striking similarities between them. Calls himself Thor? Check. Magic hammer that sprouts lightening out of nowhere? Check. Well golly gee. Superman being the bright guy he is won't attack Thor. He knows he's very vulnerable to magic. So why the heck would he attack a god with magic. Instead, Wonder Woman will attack Thor. Why? She's resistant to magic. She'll last a hell of lot longer against Thor than Superman. Will she win? Most likely not.
Now lets stop a minute and go to the battle between Captain America and Batman. Both of their respective teammates know better than to interfere with their battles so its logical that they will butt out. Both are very good fighters. Both are master tacitians. However Captain America has a indestructible vibranium shield. And Batman has a truckload of gadgets. A casual observer would say that Cap would win because he's stronger, faster and has a indestructible shield. Right? Wrong. Captain America is a very honorable guy. Batman is cheating bastard. He does not know the meaning of fighting fair. Cap would try to knock out his opponent the conventional way. But Batman doesn't play fair. He plays to win. No matter how. Alot of the batarangs would surely be deflected by Cap's shield and uncanny prowess. But Batman has other things up his sleeve. Like ultrasonics. Like vomit gas. Like tear gas. Like disorienting flash pellets. A whole lot of toys. Will Batman use them? Hell yes. While Captain America is puking his guts out, reeling from the ultrasonic barrage, blinded from the bright flashes, and crying like a girl from the tear gas, Batman swoops in and administers a blow to his solar plexus rendering him unconscious. Batman does not play fair. He plays dirty. Cap loses.
Now Iron Man has to contend with the Man of Steel, while Thor dukes it out with Wonder Woman. This is obvious. Iron Man loses.
Now Wonder Woman has been putting up a great fight. But's she's not quite as strong, or tough, or skilled as Thor. But she lasted longer than Superman would. All of sudden a red and blue blur hits him from behind. What's that? It's Superman. Poor Iron Man has been reduced to scrap metal in mere seconds. Now Thor has to battle the combined might of WW AND Superman. Thor puts up a great fight but he ultimately loses.
DC's Big Three Win