It's a pretty bad game, but compared to some of the other tripe that was coming out back then, I don't really think it could reasonably be called the worst one of all time or anything. I listened to a very interesting (but, now, sadly-unfindable) podcast with Howard Scott Warshaw, the guy who programmed it, and he's clearly a very passionate, skilled, intelligent guy. (He was a very high-ranking developer at Atari who also created Yar's Revenge.)
Warshaw actually had a lot to say about the game's world design, which was extremely ambitious at the time (it's a cube of seven screens that "wraps around" itself), and he really did seem to think that with just a bit more time, it would have been well-received. I don't know if that's true, but it definitely wasn't just some slop knocked off by people who didn't care.
And, seriously – what the F were people expecting from a game based on E.T.!? Some kind of video masterpiece!? Even that stupid Atari Indiana Jones game makes you use two controllers at once! I consider the 2600 port of Pac-Man far more offensive.