I have always had the habit of quickly editing the query if the top 5 results aren't what I was looking for, up to the point where I don't even really think about it, just adding some more keywords or sprinking a couple pluses, minuses or quotes. So I can't really tell if it has deteriorated in the past years.

However, I do think it could be possible that the pagerank algorithm does not scales good enough for the growth of Web pages, and especially with the "SEOs" out there always trying to come up with new ways to game the system.