Excellent question, though I'm not sure that is what's at issue here.
Just to play devil's advocate, it could be argued that the Wikipedia page in this case is the little gem, and that it outranks the Google pages because the Google pages are basically corporate fluff. The Wikipedia page provides first a simple description and then some more complex mathematical details, and it's a genuinely useful page.
The Wikipedia article is also on a more trafficked site than Brin-Page "The Anatomy of a Search Engine" article is, so it outranks that as well. Maybe Google should consider buying some links. ;)
PS: It might also be argued that if Google hadn't muddied the waters with the nofollow attribute, the Wikipedia link to the Brin-Page article might be kicking it up to #1.
[edited by: Robert_Charlton at 6:56 am (utc) on May 1, 2007]