True, it's grammatically incorrect. But let's face it, he was understandably excited while standing on the
moon when he said it. It's one of the best lines in history. If we could turn back time, what phrase would better sum up the moment better than that line?
It could have been worse. He could have said, "meh. It looks pretty much what we thought it would look like. Don't bother getting out Buzz, we're going home."