Alright then, a few things (some of which I forgot to mention in the beginning)...
One thing is that this debate WAS in only 3E, not 3.5. I remembered this because of my second thing, which is that we agreed to only use the core books, so nothing from the Complete books (or rather, the 3E splat books) is allowed.
Psi, I never thought about the shapechanging thing to avoid the stuns, but that's a really good point.
Thanee, I love you. Did I ever tell you that? Concise, good stuff, which I also love. But 100% of the time?
However, if the Wizard underestimates the Monk, he may wind up losing the fight. Using anecdotal evidence: The evil demonologist PC was looking for a virgin sacrifice to Grazz't and he came across a girl with one of those poles with two buckets, one on either end. He was a 15th-level Wizard, and he didn't know it, but she was a 6th-level Monk. He needed her alive for the sacrifice and he thought she was a commoner from her dress, so he started with a weak spell, with no real buffs up, and she smacked him upside the head with the bucket-pole several times and managed to kill him. She was promptly sainted by the local church.
It was agreed upon that we would build our characters specifically to fight each other, including the purchasing of magic items and the memorizing of spells, which means that They both know what they'll be up against (except specifics like stats and items carried etc...), and they'll be fully prepared for the fight ahead of time. This takes out a lot of answers that a few others have given as well.
a Monk made solely for a dual vs a wizard would have a chance...and a good one.
with improved evasion.. high saves.. some good items.. and he is untouchable from anything that allows a save.
Monks usually have a higher initiative first too...
And a monk got something called spell resistance.. that will make some of the wizzies spells fail.
I disagree with most of this. While I agree that the monk would have a chance, I wouldn't go so far as to say he has a GOOD one. Considering the evasion and saves argument, Fizdabulous' save DC was at 33-38 or something, requiring, like I previously stated, the monk to roll 18s to save against the level 9 damage stuff, which isn't likely to happen too often.
The one who goes first wins.
I also disagree, I would say that the wizard still has a decidedly high chance to win even IF he loses initiative, while the monk's survivability drastically lowers if HE loses. I also disagree with the "Same CR fight" post, 50% doesn't seem logical to me.
So let's do this, here's 2 examples, and you guys can tell me what you think:
1) Everything I said above, where the wizard and monk are both built to fight each other, and are totally prepared on that day with everything they need. In addition, they start on the Prime Material Plane 200 ft. away from each other, neither surprised. Considering that initiative has NOT been rolled yet, who would win?
2) Same example as above, but the builds are average - meaning the wizard has all the "typically good" spells in the book, and they both have magic items that just make them a "better wizard" or a "better monk" (as opposed to a wizard killer or a monk killer). They start under the same circumstances. Without going into a debate about which spells are the "typically good" spells and such, would the outcome be any different than the above example?
In addition to all this, I'm still wondering why so many people think Monks are underpowered, because even though I think the wizard would win in the above situations, I can't think of any other classes that would stand a chance one-on-one against a monk.