Preventing piracy is impossible. I worked for a company called Freeloader who bought publishing rites for games that were about 1 year old.
I was given a copy of the game (usually from HMV) and had to remove the anti-piracy code, split the game into downloadable modules, insert our own code, then upload it to the website.
It took me between 5 minutes and 5 days to remove the copy protection depending on how seriously the coders took the problem.
Interestingly the companies that went for a commercial anti-piracy system were the easiest to hack. Once you had worked out how the system worked on one game, you could use the same principles on the next.
On the resale issue, I think if developers wrote better games, there wouldn't be an issue with resale. If the game was good enough, you would want to hold onto your disk, not part exchange it on the next game.