If you’re interested in games as a business rather than just a pastime, Purple Pawn’s annual look is well worth reading. It takes a while to collate so this latest one is data from 2013. Some interesting nuggets in there.
Rather than link the pdf, I’ve linked the site as it’s worth exploring 🙂
Quirkworthy 
It was pretty interesting to see that Pathfinder sold more thn twice as much as D&D, pretty impressive!
As the summary mentions, D&D 5th ed is due in the summer and has been in open beta for a while. I suspect that by next summer the ratio will have come down a lot.
Also, as 5th edition is near, there have been no more new release for 4th edition for a while now, and new players are probably waiting for the new edition too, so Pathfinder doing better than D&D last year is nothing suprising, it would be like comparing the sales of a Warmachine new release with those of Warhammer 40k big rulebook the month before a new edition is to be released.