I think it's more a question of markets. Kickstarter aims for a far smaller market of educated die-hard fans. These huge Kickstarter records are in big part due to a limited set of fans who are willing to pledge 10.000 or 20.000. At a rate of roughly $30 per game sold (for traditional publishers) that equals to more than 600 sales for one user.
In addition to that, the budget for the game is greatly decreased since there're less marketing costs.
Traditional publishers, in contrast, try to aim for a huge market, and then also need to market to that huge market. The broader the market, the simpler the game has to be. Angry birds is a good example of that.
Disclaimer: I'm currently working with friends on a game too that, much like Angry Birds, is a easy to understand simple game idea that tries to appeal a big and broad market. I'm a huge fan of insanely complex games like dwarf fortress, minecraft, or (hopefully) the upcoming notch game, though.