Nope. We aren't the ones with the extraordinary belief in a divine supernatural creature. The ONLY reason we haven't locked up ALL the Christians in the loony bin is because to prove clinical delusion, you must prove that the object of the delusion doesn't exist. Trust me, if we could disprove God's existence, we would have grounds to have every theist committed to an asylum. But we can no more prove God's non-existence than you can prove that He DOES exist.
No...atheism is not a delusion...however...there are most people out there who believe in some guy who apparently died and came back to life and healed the sick and built buildings for his people to worship him and wants your money...yet he was sold for money which makes it really stupid.