The game is so far unplayable for many users - to me that makes the product defective - it may run partially, but if it's not playable what have you purchased? An expensive demo? Or a coaster?
It doesn't matter if the game is opened or not. A store's policy is not above a product that doesn't work. For instance, if you go to a store with a policy of not returning opened items - that does not give them any right to sell products that don't work. If you go to a hardware store and buy a vacuum that doesn't work, they are legally obligated to "repair damages" (give you a working product or return your money) even if they have some "policy" about the fact that you opened the product. Of course you opened it, you were working on the assumption that the product would be in working order. Legally, a store's "policy" doesn't mean anything believe it or not.
I guess my real point here is when do these problems stop? Games seem to be getting more and more glitchy. Before we were all hooked up to the net there were no "patches" for console games. The games came (sometimes with a few glitches) basically as finished products. I don't think that's too much to expect.
While I appreciate the direction you are taking, it is not up to the retailer to model the condition of the game but in fact it is the designer at hand. Your vacuum anology is rather hole-ridden in the fact that if it was faulty the retailer provide a guarantee or servicing availability which is to in fact cover any problems the customer experiences - these at most are because said items are expensive i.e televisions/machines/electronics. After all say Dyson package their vacuum off, once the retailer i.e Comet/Currys/what-have-you have purchased it to retail it is under their juridiction and not Dysons -to a degree.
Games have not and never have fallen under that policy, in being a little naive you could say the patching system is your guarantee. The reason that game retailers employ a no return policy on opened games, from my opinion, is in fact that these retailers would have to go to excruiciatingly time-consuming approaches to ensure that the game you have returned is in fact still under the rights of re-selling. Of course it is pretty naive to say that PS3/Xbox360 games have been altered but PC games undergo mods that the majority of users won't know how to return the game back to it's originality thus breaking the policy of being able to re-sell it. Please note I am fully aware that there is a major distinction between pre-owned and returning a game full-value, basically the customer buying the pre-owned game has to be aware that someone else has used it.
The opinion your taking of game retailers, or retailers in general if I have understood you correctly, is superficial - business is too cut-throat to accept losses and major losses at that to simply decree that they will return any item to ensure their customer is happy. Obviously the item in question is the primary factor, for example you can return clothing within 28 days where I stay and that is most likely because clothing is easy to accept and re-sell under the condition that it is still in good condition. Basically the retailer would check it and accept it back if it still matches the same item in their stock. Think of it this way, why can't you return underwear to stores.
Your grievance is well-understood but mis-directed, it is in fact the developers of F:NV that you should be crying foul of, not the retailer.
Reno