If you are actually putting quotes around those searches, that’s what your problem is. Without the quotes, the very first hit on your first one is wikipedia.
Hmmm… looks like this could be an example of Filter Bubbling.
You might want to test this by using ‘duckduckgo.com’ which does not apply any filters to your search based upon your previous searches and/or social networking.
If you want to check that this site is indeed in google, search on:
site:boards.straightdope.com crozet islands
and so on. Searching with “SDMB” in the search key is looking for pages which actually contain the word “SDMB”, which may not necessarily be this site, and this site may not come out at the top of the list.
Are you signed in to Google? If so, first of all, check your settings, and then maybe log out, and try your search again. As Gagundathar says, this may well be a personalized filter bubble effect (although it seems like it must be the filters going wrong in some way).