This is 180 degrees removed from my experience. Of all the retailers I know of (in Houston, Winnipeg, Minneapolis and Edmonton, so by no means every big market, but a pretty decent sampling I should hope), I can only think of two that sell RPGs without also having a substantial amount of space devoted to boardgames, in many cases ranging from ancient Avalon Hill ones to the latest German stuff. One is pretty clearly a labour of love for those who run it, and the other is part of a big chain that specializes in other things entirely (magazines, first and foremost), such that it's the RPG selection they carry that's the surprise.
Compare that to the number of retailers that sell boardgames but not RPGs - namely, every toy store there is, including huge international chains like Toys R' Us (and those guys do carry at least a little of the more hobbyist-oriented stuff), and I think it's safe to say there are substantially more boardgame than RPG retailers. And that's ignoring things like Jogo stores and an increasing number of FLGS' that carry both, but with a decidedly heavier emphasis on boardgames.
And boardgames taking up more display space than RPGs? Not if you're doing RPGs right, they don't. Consider the number of supplements even a middling RPG like Mongoose's Babylon 5 one supports, and you quickly realize that RPGs are about as space-consuming even if you display spine-out by default, and vastly moreso if you're displaying the covers of even a significant minority of your stock.