To be frank we've seen that quality games do sell. If a 3rd party publisher could actually be bothered to put out a Wii game that wasn't a cobbled together piece of trash hastily assembled by their 10th tier developing team, then maybe it might sell well.
People are discerning when it comes to spending money. If a 3rd party makes a game with shoddy graphics, terrible gameplay, and which is buggy as bayou in summer, then they've only got themselves to blame when it sells terribly. The reason Nintendo games sell is because they are fun, well-polished, and show the time, resource, and effort that was put into them.
And as for the whole casuals vs hardcore. Get over it. Casuals outnumber hardcore gamers by so much it isn't even funny. Even if they buy less games the industry NEEDS them to grow and sustain itself. Does anyone honestly think everyone who bought HALO 3 was a "hardcore" gamer? And what about GTA? Are all the people who bought that hardcore as well. Not a chance. Casuals drove the market's growth and they're here to stay. And casual though they may be, they can still see when a game is terrible. I don't need to be an engineer to tell you when a pipe has burst, do I? I just look at the puddles of water on the ground. All casuals have to do is give them a game a go. If it's terrible they'll work that out themselves. Casual does not mean stupid.