One way to get your website listed by search engines is to ask other relevant websites to link to your website. Search engines will follow the link, find your website, index your website pages.

Another route is to submit your website to the Open Directory Project at http://www.dmoz.org/. This is good because some other search engines use ODP data in their listings [it also gives your website greater 'credibility']

Search engines like google now start crawling from trusted sources like well known hosts. If your site is hosted on a good web hosting company (not blacklisted) you don't even need to get a link from a high PR website, Googlebot will crawl the host's index and will include you in their results (with a good SEO practice) depending on it's relevance to Serp's.
Of course it's better to get links From High PR websites, but your theory of "this is the only way" is dumped by the results i've been having with my customer's websites.
I've been trying to implement SEO practices on my customer's websites before they get crawled by the Robots and after 3 to 10 days they found them, so i had decided to plan SEO before i even let my customers purchase their domains.
Sorry for that, but i had to comment about this topic, not to offend anyone but SEO changes everyday. I would like to invite anyone that has comments about google search to post here and make this a nice thread.