This is quite a difficult thing to build. Google has a whole web spam team dedicated to trying to fight SEO.

I have been thinking about this recently. That applies to physical products too: the highest quality products are usually not the ones with the best marketing. What we need is a SEO-resistant search engine (for tutorials, products & services). Maybe a way to approach this would be to have the engine function more like an independent amazon-review engine where it's really hard to put fake reviews and have a "quality index" that's community based. I think that the successor to google will look like this: a search engine that cuts through SEO and marketing, and shows you the actual good stuff.