Long story short, it had long been urban legend that Atari buried thousands of copies of ET for the Atari 2600 after the game flopped. It's considered by many to be possibly the worst console game...ever.
Having had it myself, I can verify it was indeed awful. Worst ever? Not sure about that.
I wonder if they'll find any of the Swordquest games too?
I second the mentions of Tales of Symphonia and Skies of Arcadia. I also really like Baten Kaitos, with its crazy collectible card-driven combat system. Just make sure you turn off the voices, the actors are painfully bad.