Content is important. Content is very important. Sites that succeed generally have good content.
But...is it "king"? No.
Exhibit A: The hidden web, or deep web. A very large percentage of content (usually accepted as the majority of content) is inaccessible via the search engine route, either directly or indirectly via hyperlinks from various results.
Many of these "hidden web" sites contain reasonably high-quality content, moreso than the spammers that get in, but aren't visible simply because there's no easy way to get at them.
Here's a classic example:
This was a site I did recently for a daycare center, on behalf of an ad agency.
Is there content there? Yeah, there's some. Not a lot, but a couple of pages. Certainly more content than a scraper site, I would say.
Would there be issues in getting this site indexed? Yes, there would. And I know some of you SEO types would cringe in horror at this, but it's very much by design. Without getting into too much detail, daycare centers in Ontario have certain limitations as it pertains to space and the number of kids allowed in the facility that are individually assessed. In the case of this particular agency, the number of kids allowed isn't very high and they don't have the funding for future expansion (they need to max out the daycare center first, roll their pennies, and possibly expand uptown from there.)
Yes, I could have put info into the alt tag of each "content" section to ensure that it could still be read but I was specifically asked not to.
So the "content" is not king. This site would never get found in SEs (although it's set up to at least be indexed, should the client ever need to change their mind...by the way, the site's on its own dawt com but I can't link to it for ad agency type reasons).
In this case, content + offline-only marketing plan + ensuring that the right amount of traffic, no more, no less + using the website as a means of reiterating their primarily-communicated offline message = king.
Many web hosts in the Greater Toronto Area (GTA) employ the same types of tactics; they advertise in various offline channels, mostly because their pricing and service is so subpar compared to their global counterparts that they don't want to end up "overexposed" and deal with the resulting negative feedback.
There are quite a few websites besides hosting companies and the downtownkids website in the GTA, although the latter is the only one that I know of that has a legitimate reason for the design and development tactics employed.
So yes, content is important, but if your marketing plan doesn't work for you, then your content is pretty well wasted.