The reason they don't work is because the NES's cartridge connector was poorly designed, and wears out quickly. So the pins on the the cartridge don't make good contact with the connector. The lockout chip is what causes the blinking. If there isn't a good connection between it and the game, it will keep on blinking. So, to fix the problem:
1. Replace the cartridge connector.
2. Disable or remove the lockout chip.
Just replacing the connector should help a lot, but if you disable the lockout chip, it will run even more stable.