I'm seeing a lot of pages of big, authority sites, ranking very high in the SERPs. When infact the links to that page are very low, the PR of the specific page is low, the on page optimisation is nothing special and so on But still, i guess, because of the main site, the rank pretty high. My queston is, does a whole site optimised for that only niche has a chance against a single page, but a page from a big multy themed, authority site? In case that i can outplay the specific page off and on page optimisaton, but no chance to compare to the backlinks and SE power of the main site? In my specific case, the main domain of the authority site has like 100 000 backlinks, when the page they have for my keywords has like 100 or so links.
Yes you can compete if you theme an entire site around one topic that represents only a few pages on some other multi-theme site. I've done it. Build out your site in a good hierarchy with the main keyword as your home page, branching down to sub topics from there (where you use the main keyword as part of each page's them where possible). Then start getting links for the main topic on the home page and try to get some links to the internal topics too. If your content is good you should be able to attract good links to your pages and win the race.