The extremely short answer is...
Now as for movies, you might say "Ok, here's a pretty comparable market. Movie budgets are comparable to video games nowadays and DVDs and BluRays are a comparable product since you might buy it and consume the experience once or twice before you're done with it. Why don't they complain about the used market?"
. That's because movies make the bulk of they're money on their theatrical run and the home market is just bonus to studios. It's become a bigger and bigger bonus over the years but all it really is in the end is an extra revenue stream for that product. Again, video games don't have that.
Why No Analogy Works
Again, no analogy works because no other industry has a Gamestop. There isn't one other industry where one company controls 21% of the market and consistently pushes the used version of the product they specialize in over a new one when the used version is an identical experience. That's why it just doesn't compare. That's why developers bitch about it.
So let's get some more shit out of the way.
"Games cost too much. Why don't they lower the price of games?"
Because those giant games you love so much (Uncharted 2, Halo, Metal Gear Solid, Call of Duty) cost a fuckton to make and unlike movies, the only money they'll ever see from it (until digital distribution is cemented at least) is if you buy it new. If you want significantly lower prices, than expect significantly different products whether that be shorter games, lower budget games, etc.
"If Gamestop is making so much money, why don't the publishers start their own stores?"
Are you fucking serious? Do you know how small the commercial viability of a Square/Enix store would be that only sold used and new Square/Enix games? Do you really think they could compete with Gamestop at this point because they would have to.
"Well they should provide more incentive for me to keep the game longer."
They are. That's why almost every game has multiplayer nowadays whether it makes sense or not. That's why almost every game has DLC. There really isn't much more they can do other than that. You're basically asking why movie companies don't provide more incentive to keep a DVD past your one viewing of the movie.
"What's the solution then?"
Ultimately there's only a few of options here. Digital distribution is one but a lot of you want physical copies of things. Developers getting a cut of the used market is another but a lot of you seem to have a problem with that as well. Publishers selling the games to retailers at a lower price point could help in discouraging them from pushing used so hard but I don't know if that's commercially viable for them (that could be another topic on its own). So yeah, if I knew I'd try to get the word out but the situation at this point is pretty complicated.
Do I want to see the used market go away? No. Are developers completely against the used market across the board? No. But you are kidding yourselves if you try to say any other industry is in the same boat. Gamestop isn't evil. They're just a company like any other trying to make as much money as possible but the way they're going about it at the moment is eating the industry from the inside and ultimately it's unhealthy for it as whole. You can't be pissed off at developers for that.
LOOK WHO CAME: