I see little wrong with Vs. threads for the most part. Hey face it, we're all huge nerds, and this is one of the things nerds do.
Strictly speaking I do not think the two would fight each other as I'm pretty sure they have teamed up in company crossovers in the past.
When dealing with Batman in paticular, it all depends on the circumstances of the fight. In general Batman and Iron Man (marvel) both have a habit of losing the first round against many of their more powerful enemies. Then they go back to their base, and gadgeteer a solution to whatever beat them/drove them off so they win in the end.
Ironically though people tend to forget that Spider-Man is ALSO a gadgeteer and while it's not as typical for him, he does the exact same thing. He'll like lose a fight, get a skin or bloody sample (or whatever) head to the high school (or college) chem lab and whip up a serum or whatever to help him. I do think he's generally on a lower "tier" of gadgeteering though.
In a straight up fight, based on an initial encounter I think Spidey would win. In an overall context of who wins a "war" made up of multiple encounters... well that would probably be Batman as he maxxes out higher on the "able to adapt to opponents" chart.
As far as Batman beating Superman with kryptonite, that's debatable (in response to come of the comments). People tend to referance what they have heard about the old "Dark Knight Returns" storyline by Frank Miller. The thing is though that for those who read the book, it's stated very specifically that Superman threw the fight. In fact that is what the entire story was leading up to. It appeared that Batman knocked him out, and then died from cardiac arrest after winning. However Superman made it quite clear that he was playing possum and what's more could tell that Batman's heart was still working. So basically what Batman did was insufficient including the use of Kryptonite.
More recent events within the actual DC continuity have Batman using kryptonite to win quick scuffles. A sucker punch with a kryptonite ring, or a plan stolen from him by Ra's Al Ghul being implemented by The League Of Assasins in "Tower Of Babel". It should however be noted that both stategies involved surprise attacks (like most villains who used Kryptonite on Super Man). In general people tend to forget that unless you can get it into proximity with him Kryptonite isn't anything other than a fance rock. What's more Superman has in the past used powered armor and radiation suits to deal with it when he knew what he was up against (or at least I vaguely remember him doing so). So really if Superman ever TRUELY desired to take out Batman, he knows Batman has Kryptonite and would plan accordingly. Heck, he might just send a Superman robot double (one of the things people tend to forget about, Superman is a scientific genius w/ access to alien tech to boot, and has been making robots and stuff since he was Superboy).
To be honest this is not to say that Batman couldn't beat him, I mean heck Lex Luthor who has no powers of his own either had won rounds against Superman, and almost killed him on like a billion occasions (Superman has needed to be rescued by other heroes... a lot). But to be frank he wouldn't be able to do it in a typical Batman fashion. He'd pretty much have to set a trap and genuinely catch Supes by surprise.
