Okay a few things to the original argument (You have no right to complain if you buy used.), and skipped a few pages of posts here so if this has already been said, so be it.
1) THIS IS AMERICA!!! And as an American (well North AMerican in my case) I have the god given right to complain, ***** and moan about whatever I please. You have the right to Ignore me. If I buy a game New, used, got it as a gift, or didn't buy it at all (went to a friends place and played it there), I have a right to complain about what I experienced. I also have the right to form an opinion based on watching a youtube video and then Yahtzee's review....that opinion would likely be termed "Second hand" or "Ill-informed", but its my right to be that way, and to complain thusly. I therefore complain that the little goth girl shows up way too much in Bioshock, and the game would be way better without her! (I've never played it so take it for what its worth)
Conversely, you, and others have the right to ignore me completely.
Ain't freedom grand?
2) The Game developer DOES NOT HAVE TO listen to customer. Once a game is released, they are well within their rights to say "That's it, don't call us, we be done"
Now for future customers they might want to garner some goodwill by, you know, making current ones happy. THis is the internet age, and word travels fast when a company is known for a shoddy product and even worse after market support.
AND here's a crazy idea. If a Developer makes a game, gets feedback, maybe they can use said feedback and MAKE IMPROVMENTS TO FUTURE GAMES! User input can (and should) be very important to software development. Knowing what your end users want and like and don't like can assist in making software BETTER, and thus more appealing for future users.
3) GAME COMPANIES SEE NO MONEY FROM USED SALES. Not always.
True if I buy Fallout 3 used (as I did) Bethesda sees not one red cent. But when I enjoy the game and buy the DLCs, or am encouraged to buy Fallout New Vegas as soon as it comes out, isn't that a residual sale that I likely wouldn't have made if I hadn't rolled the dice on 20 bucks for a used game (And actually My Fallout 3 was stolen long before I finished it so I bought the GotY edition new, but that's an odd case).
4) Why are Used games so different than used other things? Houses, Cars, comic books....Spider man's first appearance was in a 12 cent comic, I don't hear a lot of crying about how poor marvel gets nothing when someone buys it now for 20 grand. Some cars are worth far more now than they were originally, do we lament for poor Ford? And more importantly if you don't buy a Ford, are you no longer entitled to say you think a particular model looks stupid? For that matter, and going by this logic, when the Wii came out, you had no right to complain about the dumb name unless you bought it?
5) As a consumer I pay goods and services a fair market value. I like sales, but failing that I am willing to accept the Market's wisdom in setting a price. The understanding, of course, is that when I, and many other gamers pay $x for a game, some of that cost is going to pay for the original development, cost of the physical packaging and game disc, box art, shipping to the store, store's overhead, etc...and in the end, hopefully some profit for the devs. Now if I buy a direct download, where there is NO physical cost, and presumably far less overhead cost, why do I pay the same, or (as I've heard people say) more?
As well, if I buy Used, the devs may not see profit from MY purchase, but they got profit from the original purchase, which I have now payed a portion of, think of it not as buying used, but as a Time Share!