Richard Dawkins answers the question in the Washington Post:
No. As the College of Cardinals must have recognized when they elected him, he is perfectly – ideally – qualified to lead the Roman Catholic Church. A leering old villain in a frock, who spent decades conspiring behind closed doors for the position he now holds; a man who believes he is infallible and acts the part; a man whose preaching of scientific falsehood is responsible for the deaths of countless AIDS victims in Africa; a man whose first instinct when his priests are caught with their pants down is to cover up the scandal and damn the young victims to silence: in short, exactly the right man for the job. He should not resign, moreover, because he is perfectly positioned to accelerate the downfall of the evil, corrupt organization whose character he fits like a glove, and of which he is the absolute and historically appropriate monarch.
No, Pope Ratzinger should not resign. He should remain in charge of the whole rotten edifice – the whole profiteering, woman-fearing, guilt-gorging, truth-hating, child-raping institution – while it tumbles, amid a stench of incense and a rain of tourist-kitsch sacred hearts and preposterously crowned virgins, about his ears.