I agree, I've found plenty of freeware games that are worth playing and plenty are way better than titles available at stores. I'm also pretty sure most of the people who feel new games are too expensive avoid buying them. Excluding portable systems, the most current system I have is either the PS1 or N64 and I got those used, I pretty much just stick to the older systems. There are several current games that interest me, but I'm not going to buy a new system just to play a handful of games on each of them.
It's because most people already have the classics in their collections, they've been in print long enough for most people to have already owned them at one point. They are still popular enough to be in print though, and I'm sure if new books are written well enough they'll also stay in print long enough to become classics. They're not best sellers anymore but they still bring in money. You really shouldn't compare the percentage of sales of the publishers when what counts is what each author gets. Count how much money an author(or their estate) got since their book first got published, if it stayed in print for over 100 years that would still be more money than what a best seller would get if only in print for 6 months. Think of each game developer as an author, not a publisher. The better the game the longer it will stay in print and the more money the developer will get.
If the games are good enough they'll still sell. Seeing a movie once in theaters is about $10-$15, while getting a new game to play once is around $50-$60. If people like the movie they'll buy the DVD so they can watch it over and over again. Sure you can play the game more than once since you've bought it, but you'll only want to if it's good enough. If it's bad, there's a good chance you won't even finish it once. If more people felt that the games were good enough to keep playing, they'll be willing to buy a new copy rather than a used one. Plenty of people buy a used copy, play the game until they get bored, and trade it in again. Who cares about condition if you're planning to sell it once you're done? That same used copy can sell over and over again if it keeps getting traded in, to prevent that from happening make the game actually good so it won't get traded in. The more it sucks the more people don't want to keep it so it becomes available to buy used.