@Nutboy: Well, I basiclly agree with you. Wii did expand the market but not to extend most people on vgchartz belive. Most people can only give you anectodal evidence that Wii actually changed the market but when NPD says otherwise I'm going with NPD.

But you did make a mistake when calculating number of new video game users. GC/Xbox/PS2 groups aren't disjointed. So you can't simply add numbers of users that "upgraded" from PS2, Xbox and GC. Lots of GC and Xbox owners also have PS2.
But NPD data still shows that most of Wii succes is build on PS2 userbase.

More than likely most of the growth is coming from the DS considering more than one person in the house will own one. However I think we'll see some more expansion in the console world of America due to the Wii as it's probable that not all gamers of a younger are live with their parents or family... or that families before even had a console. I mean it's something that's hard to comment on.

I feel the best way of knowing of someone is expanding a market is by looking at the competition. Why? Well if someone is selling at unprecedented rates then if nothing was expanding then the other consoles would be doing exceptionally bad. However both 360 and PS3 are able to thrive in a market considerably dominated by Wii suggesting that Wii is expanding rather than taking sales away from PS360. Now it's not saying Wii isn't taking sales from them, because they are, but that's not the only place where its generating sales.

My best friend and a dude from my work have Wiis and didn't own PS2.

I would say it has expanded the market, but at the family level, that is, more people of the family are playing it than did the PS2. Primarily you know this because of the games of Wii Sports and Wii Fit are more universal to pick up and play than probably any PS2 game, not to mention the ease of the Wii controller vs a 'standard' controller.

The other thing we don't know is how many of the GC and Xbox owners also owned a PS2. If all of the GC and Xbox owners that have now purchased a Wii, had owned a PS2, then they are already 'counted' in the 8M. And the 3.4M would be all new gamers. Of course, that extreme is unlikely. But say, 25% of the GC and Xbox owners bought a Wii, but of that number, 80% also owned a PS2. That means only 5% of the GC/Xboxers (or 1.25M) are ones that bot the Wii, but did not own a PS2. Leaving 2.15M as completely new gamers. About 20% of the total Wii gamers.

 This is obviously the correct explanation.

 25M Ps2s * 20% = 5M

The logical would then be ~ 3-4M GC owners, with a 1M ish overlap, so 2.5M there, and a bit lower from XB, maybe next to none really.

So that would bring the total up to ~ 7.5-8.5M, meaning that Wii really has a somewhat of 33% new buyers in Americas this far.

All I knoe, is that when I was trying to buy Wii Fit, people who probably never played a videogame before in their life were waiting in line to buy one.

This fills me with mixed emotions.

but either way the point is, that yeah I think it expanded the market.