^Game Party is also only £15-20, same for Carnival games.

Personally I think that being the Number 1 console with massive hype overall is moving all Wii software more than it might otherwise. 3rd parties and even Nintendo have yet to invest massively in promotion for Wii games.

On the PS3 all games are going to struggle due to a small userbase.

The 360 has only a medium size userbase but those users buy lots of games. Problem is there is a huge library of existing games and many quality games already available. Additionally 3rd parties are throwing a huge amount of money at promotion for these games. And games are having a hard time standing out when the genres are already well represented.

You also forget that Nintendo is moving to a 6 months promotion timeframe for their games, while 360/PS3 are seeing the hypetrain go on for 2-3 years beforea game is released.

Its all because of the new casual gamer adience that nintendo has drawn in.

Its not really a surprise when a Wii game sells a million

From what Ive seen, a lot of people go into stores with their kids or w/e and pick up 1 or 2 games.

 This, basically. A larger percentage of Wii owners than the other consoles don't readvideo game magazines, or go to enthusiast sites. If it's not on TV, or mainstream magazines, they don't know it exists until someone tells them about it. This word of mouth takes time, but it's ultimately more effective at selling stuff.

I'm just waiting for the day that more Wii publishers start pimping their wares on Home and Garden magazine in addition to EGM... 

^^ This is why Nintendo have upped their tv ad budget as it exposes both casual and core gamers.

 True, and it seems to be working, as their current generation of games are often outselling their predecsessors. But a lot of other publishers either won't, or simply can't, afford to advertise widely on television yet. In fact, with five exceptions, I can't recall any publsihers airing TV ads during prime time, when they'll get the most eyeballs. And if they have, then it seems they're doing it wrong, since I can't remember.

Either way, I stand by my earlier answer...until someone points out the blatantly obvious thing that I know I'm missing. 

because many are casual games and casual games typically arn't hyped

It's simple, casual gamers don't f* care about hype, actually, they usually don't know about hyped games. They buy games they think they will like or that other friends liked. Not to mention that casual gamers are the mass market.

In PS360, there games that please most of the core gamers. But, in the other hand there are many core games that appeal only to a small amount of gamers (niche tittles) - that implies in low sales.