Problem with HMV specifically is that they tended not to update their in store pricing when reducing stock online. So you could pick up a DVD boxed set online for £9 which in store would be sitting at £39.99. Partly down to them individually pricing items rather than by shelf/area like supermarkets do and having rather chaotic layouts and being forced into low level displays so people are able to browse. Their produce per square meter must be very low compared to even a standard book store.
I've been in them recently and never once seen anything I couldn't get far cheaper online, it has to win on convenience which when you walk into an HMV you don't get due to having to find the damn thing you are after, which invariably isn't in the area is should be or is only available on the chart display and you've been looking it up under the band name.
I can see many games retailers going the same way, there's far too many stores dedicated purely to console games now, I don't see how they make a profit.
It's a real shame as HMV has a very interesting history behind it, but it's now just a badly run "discount" DVD store.