Hi, Gary! Glad to hear from you!
You are right, anecdotal evidence is worth very little -- your experiences in the "D&D heartlands" as it were, versus mine in the Bible Belt ran quite differently. What I would be interested in, were such a thing were ever available, is the size of "networked" gamers now versus the early 80's, whether the internet makes a big difference in the network size now versus then, because the number of dedicated gamers is roughly equivalent to the number of those who participating in networking - to me, this stands to reason, because the more serious you are about your hobby, the more time you invest.
I know for sure that in my area, I know far more gamers now than then - and the ones I know I keep in touch. My experience runs exactly opposite to Diaglo's: Back then, I knew all of one other solid gamer; now, I have had groups ranging upwards of 13 people at the same game! My personal record for a 3E group is around 9 at the table.
Maybe we'll never know for certain - but based on sales figures alone, we know that in three short years, WotC attained numbers not seen in 20 years. In that score, good for them. I am a firm believer in that if you grow the customer base, all the smaller companies benefit by default, because a Gaming Hobbyist is usually a gamer for life, and migrates around to other systems as he looks for new products.