Evangelical Christians believe the Bible is God's Word and is without error in the original manuscripts. Muslims respect the word of the prophets, but claim the Bible has been corrupted (mostly by Jews) and is only correct insofar as it agrees with the Koran.
God calls himself "I Am" and says He is one, but with three personalities. Muslims believe God's name is Allah and reject the Trinity.
How can the president say that we all worship the same God when Muslims deny the divinity of Jesus, whom the president accepts as the One through whom all must pass for salvation? Do both political parties have the same beliefs? Are all baseball teams equal (clearly not, because only two will go to the World Series)?
The president can be commended for sincerely reaching out to Muslims, but he should not be commended for watering down his beliefs and the doctrines of his professed faith in order to do so. That's universalism. There are "churches" that believe in universalism, his Methodist church does not. No Christian who believes the Bible believes in universalism. And No Muslim who believes the Koran does either.
President Bush is wrong - dangerously wrong - in proclaiming that all religions worship the same God.