Site content is king.

[Jura]

http://www.free-seo-news.com/newsletter339.htm#facts

Official Google statement on how to get high rankings.

Inbound links are important but content is even more important
Google's Maile Ohye writes the following about inbound links in his article:
"Inbound links are links from pages on external sites linking back to your site. Inbound links can bring new users to your site, and when the links are merit-based and freely-volunteered as an editorial choice, they're also one of the positive signals to Google about your site's importance."
Nothing new here. If many related websites link to your site, and if these links look natural, this will help you rankings on Google a lot.

However, links are not the most important ranking factor. Maile Ohye gives a concrete example:
"Let's say I have a site, example.com, that offers users a variety of unique website templates and design tips. One of the strongest ranking factors is my site's content. Additionally, perhaps my site is also linked from three sources -- however, one inbound link is from a spammy site.

As far as Google is concerned, we want only the two quality inbound links to contribute to the PageRank signal in our ranking. "
The website's content is mentioned as one of the strongest ranking factors. The inbound links are additional. That makes sense. The content of your website tells Google what your website is about.

If you want to get a high ranking for the keyword "used cars in dallas" but your web pages are about microwave ovens then you won't get high rankings for that keyword.

For that reason, it is very important that you optimize your web pages for the keywords for which you want to get high rankings before you try to get links from other sites.

Google analyzes over 200 ranking factors
According to the article in Google's blog, Google analyzes more than 200 signals (we call them 'ranking factors') to specify the position of a web page in the search results:
"Given the user's query, over 200 signals (including the analysis of the site's content and inbound links as mentioned above) are applied to return the most relevant results to the user."

It's a simple two-step process
Getting high rankings on Google is a simple two-step process:
You must optimize your web page contents so that Google can find out what your website is about. Optimize your web pages for your keywords so that Google knows that your website is relevant to these keywords and your topic.
Other websites must confirm that your website is about that topic. That's what inbound links are for.
It's as simple as that. If your website passes Google's analysis of all ranking factors, it will get a top 10 ranking.

http://googlewebmastercentral.blogspot.com/2008/10/good-times-with-inbound-links.html
And another related blog post.

So how can you engage more users and potentially increase merit-based inbound links?
Many webmasters have written about their success in growing their audience. We've compiled several ideas and resources that can improve the web for all users.

Create unique and compelling content on your site and the web in general
Start a blog: make videos, do original research, and post interesting stuff on a regular basis. If you're passionate about your site's topic, there are lots of great avenues to engage more users. If you're interested in blogging, see our Help Center for specific tips for bloggers.
Teach readers new things, uncover new news, be entertaining or insightful, show your expertise, interview different personalities in your industry and highlight their interesting side. Make your site worthwhile.
Participate thoughtfully in blogs and user reviews related to your topic of interest. Offer your knowledgeable perspective to the community.
Provide a useful product or service. If visitors to your site get value from what you provide, they're more likely to link to you.
For more actionable ideas, see one of my favorite interviews with Matt Cutts for no-cost tips to help increase your traffic. It's a great primer for webmasters.
Pursue business development opportunities
Use Webmaster Tools for "Links > Pages with external links" to learn about others interested in your site. Expand the web community by figuring out who links to you and how they're linking. You may have new audiences or demographics you didn't realize were interested in your niche. For instance, if the webmasters for example.com noticed external links coming from art schools, they may start to engage with the art community -- receiving new feedback and promoting their site and ideas.

Of course, be responsible when pursuing possible opportunities in this space. Don't engage in mass link-begging; no one likes form letters, and few webmasters of quality sites are likely to respond positively to such solicitations. In general, many of the business development techniques that are successful in human relationships can also be reflected online for your site.