I doubt anyone agrees with John this time.
However, part of me wanted to see his prediction true so the rest of you can drop your jaws in disbelieve.

 The DS had Brain Age (aka Brain Training) with Dr. Kawashima, and that's the one that sold a gazillion copies and gad a sequel that is also selling like crazy.  The DS also got Big Brain Academy, which was Brain Age's cheaper uglier, smellier cousin.  Big Brain Academy is the one that got the Wii sequel at 2.5 times the price.  If a real Brain Age game came to the Wii I think it would do much better, but that would hurt the sales of both DS Brain Ages, which are both selling insanely well every week everywhere.

 Wii Fit is a different story.  When Wii Fit comes out, weird things will happen.

Well what a bold prediction... but you overlooked something. Wii fit is not just a game. It needs the Wii board! I doubt Nintendo can produce enough Wii boards on launch day to get even one third of that number. If it's gonna be a success, they will have problems keeping up demand all over again....

Edit: sorry for the double post. Problem fixed hehe.

Nintendo will not have enough Wii boards on launch. They will be taking a huge risk if they produce more than 1 million Wii boards on launch. Launching the Wii board with Wii fit is kinda like launching a new console. It has the potential to sell console-like numbers though. Meaning it will outsell Halo 3 without a sweat. Just a matter of time.

WiiFit in Japan will outsell Halo 3 in Japan opening day.

Such as WiiBoard impaling HDTV. Apparently slipped out of their feet and flew directly at their TV's.

Nintendo will soon issue a free ball and chains add-on that you can attach to yourself and the board to avoid further board-flying incidents. 

I can see it selling very well in europe ... big private channels already introduces Wii Fit in their news shows over here in germany.

Joemanji you're right, this is not only based on software but most of all hardware and its up to Nintendo of how many balance boards they can create in short notice. I dunno about sales, I have mixed feelings about this. One group who will love this, I'm one of them and will buy it right after the Japanese release... and the other group thinking: what kind of nonsense is this anyway? And then I mean with "WII owners". I think it might sell well right from the start, but outselling Halo 3 in the US in its first week? Sorry, not a chance! Outselling Halo 3 in Japan? I expect it will...

@Frank, what are you blaming WII Fit for? :D

the only way any title will beat Halo3's sales on the first day/week/month or whatever is if it launched in all regions at the same time. MS proudly announced the 360 was the fastest selling machine in history, they glossed over the fact it was the first machine to launch in all regions within a month, which is obviously going to make a big difference compared to the 12 month time difference in launches in the past.