No, God is not a failure just because there are a few atheists...
According to sociologists Ariela Keysar and Juhem Navarro-Rivera's review of numerous global studies on atheism, there are 450 to 500 million positive atheists and agnostics worldwide (7% of the world's population), with China having the most atheists in the world (200 million convinced atheists).
Demographics of atheism - Wikipedia
That means that 93% of the world population believes in God.
If God had never used Messengers, hardly anyone would believe in God because
the main reason people believe in God is because of one of those Messengers. Very few people in the world believe in God for some other reason.
84 percent of the world population has a faith and those faiths all have some kind of Founder, what I refer to as a Messenger. So obviously, using Messengers is a successful method of communication.
There will always be people who do not believe in God because man has free will so man can choose to believe in God or not. This is exactly the way God wants it, otherwise God would not have created man with free will.
Worldwide, atheism was growing at a rate of 6.54% from 1910-2010 but dropped to a growth rate of 0.05% from 2000-2010. Agnosticism was growing at a rate of 5.45% from 1910-2010 but dropped to a growth rate of 0.32% from 2000-2010. That demonstrates that both atheism and agnosticism are on the decline but also that there are many more agnostics than atheists.
Statistics from:
Growth of religion - Wikipedia