While I'm not thrilled with the current chaos is Iraq, we have ousted Hussein. That means Iraq is not sponsoring international terrorism or building wmds. That by itself is a huge success. The day we dragged Hussein out of that spider hole is the day we greatly reduced the chances of a wmd going off in an American city.
What you're missing is that the main enemy is Iran. Iraq was a target of convenience. But Iran has managed to tie us down there while they develop their nuke. When that happens, and I see nothing stopping it now, Bush will go down in history as a worse president than Jimmy Carter.