"The conventional wisdom is the U.S. mistake in Iraq was not enough troops," said Thomas Blanton, the archive's director. "But the Desert Crossing war game in 1999 suggests we would have ended up with a failed state even with 400,000 troops on the ground."
Democracy isn't a revolutionary process but rather an evolutionary one. Democracy needs to be built from the ground up and not the top down. In time Islam and democracy will co-exist but not today. We have already seen progress towards democracy in countries like Saudi Arabia, Egypt, and even Iran. The best tools for this change aren't guns but instead the internet, cell phones, satellite television etc. It is through prosperity and technology that we will spread democracy.
Of course, I would argue that democracy doesn't necessarily mean a pro-USA outlook or even peace, but that's a debate for another day.
Here is an article explaining why our chances for success in Iraq are low. Interesting tidbit is that it was written in April, 2003 just before Bush declared "Mission Accomplished."
So if you believe like I do that we can't win in Iraq, the best course of action is to pull out. At some point you just gotta realize what's going on and cut your losses otherwise, we'd still be stuck in Vietnam.