I think part of the problem is that not everyone has infinite moneys to pay for video games. Therefore, they want to buy games that they know they are going to enjoy. Games like Mario and Zelda are games that lots of people know they will enjoy.
Personally, when I hear about a new Nintendo game like Mario Kart or some such, I get really excited because often I've played a previous game in the series and enjoyed it. Also, I trust Nintendo as a company to create enjoyable games. When I look at the 3rd party games that have been announced for the Wii U, I see lots of darker, violent games which I'm just not interested in. When 3rd parties create games that I find really interesting, I will buy it.
I think that the demos that are being brought to the 3DS (and hopefully the Wii U) are a great thing to let people experience new games from other companies. They let people experience a game that they wouldn't otherwise play. This way people can find new games that they find fun.
- Hank Hill and MachineLaw like this