If 50 Websites Optimize Properly, How Is A Search Engine To Choose?

Here is the latest internal thought I had that makes me wonder what its all about.

For curved shower rod there are about 50 to 75 sellers, including myself, all selling the same product from the same manufacturer.(who holds a patent) Add to this the redundant items from these same sellers being cross-listed on Ebay, Froogle, Shopzilla, Shopping.com, etc and you have several hundred pages that are all 100% relevent ro the consumer putting curved shower rod in the Google search box.

A high percentage of my competitors have sophisticated e-commerce sites that have already done their proper SEO (keyword saturation, title, links, usability, etc). So how does Google decide which 10 pages to put first? It hardly matters from Google's persepctive because they really have a few hundred pages that would be 100% relevent and 100% authoritative on curved shower rod.

The searcher will get what they want no matter which of these few hundred pages are served first. So have we reached a point in this case where the algorithym has gone beyond its purpose and all that is left for the webmasters is to game the algorithym as more information becomes appearent? I mean, the usual advice about making the page as good as it can be for the consumer has already been implemented and it just isn't going to get much better.

Thanks,