Debbie, I am going to have to disagree with you.
I work for an Internet marketing and SEO company, and our number one focus is content. Though we spend a lot more time on actually writing content than many other do, we have become very successful at organically ranking not only sites, but individual pages (and blogs, google Knol pages, Squidoo, etc.).
Writing content for the web is quite an art, but can be mastered fairly easily. Keep in mind that google and other search engines are looking for not only your target keyword(s) but also related words and factor in keyword density (and many other things). But on that, you need to be sure to get your keywords in, but not use them too much or too little and also be sure to get your related phrases in. Use Google Keywords Tool to find related phrases.
The easiest way to check is pretty simple. If you read it and it sounds "spammy" it probably is. Find a balance. And remember: you aren't writing solely to a search engine. If the page can't close sales, it doesn't matter if it ranks #1 or 100.
Content is king, and ranking high organically can be done without ANYTHING else if it is done right.
In regards to your question: comments are a great thing. It allows the users to engage in the topic (and it also allows the users to create content for you, which can help on the SEO end).
Not quite (but very close) to social media would be websites like de.li.cious digg.com stumbleupon.com
all great social bookmarking sites that are very good at driving traffic (and relevant traffic) to pages.