Only really a failure if it didn't meet Atari's, perhaps unrealistically, high sales expectations. (I've heard the figure of millions of copies of E.T. and Pac-Man thrown in the dump may have been exaggeration. But if they did expect Pac-Man to sell to 120% of console owners, that would have been just insane.
And yet after dumping E.T.s in 1983... apparently they still made more after that. As I've seen on another forum, a guy collecting E.T.s for whatever reason, and he has some copies dated 1986.)