Interestingly enough, office supply stores where I live often have $10 re-releases and compilations that the other retailers around here don't stock. Some recent examples I've seen: Syberia 1+2 for $10 (even before GOG had them), Tomb Raider Anniversary + Legend together for $10, Splinter Cell 3 for $10, Stalker: Clear Sky for $10...
Target and Wal-Mart carry similar reissues, but their selection is different, for some reason, and doesn't change very often.

Here on the french speaking part it's exactly the opposite... It's has always been hard to find fellow PC gamers over the years and now if I may cross one there's a 90% chance they only play any MMO. On the shelves consoles games are the majority, and PC is slowly decreasing as time pass. However I actually lacks numbers to make a fully correct statement.

Here's the status of PC games that I've noticed at all the stores around here, comparing it with what I remember from around 1999-2000, when PC gaming was at (IMHO) the height of popularity:
EB Games/Gamestop/Software Etc.
Then: Entire back wall, going to the sides, filled with PC games of all types
Now: Tiny little rack tucked in the back filled with around 50 games of various quality.
Best Buy
Then: Rows and rows and rows of PC games
Now: Rough average of 3 shelves, but can vary on location. (Tualatin, OR has around 2 shelves, Beaverton, OR has around 4-5 shelves)
Gamecrazy
Then: Nothing, but then started carrying PC games behind the counter around 2005
Now: HAHAHAHAHAHAHAHAHA
CompUSA
Then: OK to Average selection. Typically had newer titles, but some older titles could be found as well
Now: A joke. Lots of casual/budget ware
Fry's Electronics
Then: PC Gaming mecca. Rows and rows of every PC game you can imagine, including some hard to find gems.
Now: Exactly the same, PC gaming headquarters for 25 years running :D
Target
Then: Meh selection
Now: Actually a pretty reasonable selection of newer games only, about 2 shelves worth.
Fred Meyer
Then: Bad. Mostly only budget titles or poor games.
Now: Actually stocking a pretty good selection, at least my local one is.

We had a Software Etc. at the mall some years ago. It was a small store, being in a shopping mall, but it was arranged into aisles for maximum display density, and it was crammed wall-to-wall with PC games (with a few aisles for productivity and utility software). I used to love browsing in there. There was also a fairly large shop that specialized in PC game rentals - they didn't last long. Nowadays, Best Buy is the only store nearby that's worth bothering with, but their selection is predictable.
One thing that irritates me about Best Buy is that they have one shelf dedicated just to Sim games (mostly The Sims 2 and 3) and one shelf dedicated just to Blizzard, even though neither of those two shelves are filled to capacity. They've got big cardboard signs attached to the top of the shelves and everything. Gamestop devotes quite literally 50% of their PC shelf space exclusively to Blizzard (at least, in those stores that even carry PC games at all). Seriously, just shut the hell up, Blizzard.

I don't see a tendency of big retailers shrinking PC game shelf space in the German-speaking region, but that's probably partly due to most smaller stores who sold games having disappeared - people who want to buy PC games in stores simply don't have a choice anymore.
There was a number of small stores called "PC Joy" who were focused exclusively on PC and Mac titles, very neatly sorted, down to obscure stuff or classics, and with competent guys who actually knew more games than just last year's top 5. They were bought up by EB Games and the stores remained, but they survived about 2-3 months and then they closed them all down. There was a nice store called Alcom that was huge, and partly specialised in rarities, imports, and games for old consoles. I hear this operation was basically run by one guy though, and since he left, they stopped doing that and by that lost their uniqueness. Big electronics retailers (MediaMarkt, MElectronics, ...) probably were able to keep their selections large because the specialised competition disappeared.
Edit: This was the shit!
http://img706.imageshack.us/img706/3226/pcjoyluzern.jpg
I remember gloating at a display window that was full of Duke Nukem 3D merchandise and boxes... but I couldn't buy it because I was only 12 =)