As a former Best Buy employee, I can take the "store by store" assessment to an even bigger way of knowing and that's based on "region". Regional managers are the ones that cast down the "heat" to stores to get them to make deals. Store by store still has its merit, but if a regional manager is really firm on policy and margin, you'll never see games, software or computers marked down.
For example, here in San Diego - In Chula Vista, you have a pretty good chance of getting a deal on an open box or discontinued computer or television. Software is almost NEVER on clearance slash prices. When the 2008 Edition Macbooks were discontinued, we sold black Macbooks (Normally $1500) were going for as low as $750 open box with full box/accessories and hardly a scratch on them. But in El Cajon? You were lucky to even get the 10% Open Box discount off the regular price, because the El Cajon managers argued that "the marked down price is considerably lower than the retail price, so they're hard to find, so even when we get open box, we put them back up to original price." As you can probably guess, El Cajon had a lot of Macbooks sitting on their shelves.
Your best bet, in all honesty, is to ask an employee if they have any "at risk" PS3 or 360 games that the manager might make a deal on. If they have boxes of stuff sitting in the back, a manager will be willing to part ways with 10-20% off.
Even regular employees can slash a product by 10% or as much as 15% depending on the dollar amount. I've taken 10% off software, games, accessories for many customers to make the deal "sweeter". I never did it on high priced items like computers or televisions because that's a red flag, but even when I took 15% off Gears of War 2 for a customer who was buying a 360, the extra warranty on top of his computer, my managers didn't really care.
So yeah, definite YMMV, but if a title's been out a while and they have a lot on the shelf and you know it's a game that doesn't get recirculated, ie. Collector Edition Fallout 3, Saint's Row 2, etc... It's definitely worth at least asking an employee if a manager will discount it.
for about $40
