Both have/had a pet issue that they were sure they were right about.
For Bush, the war in Iraq. For Obama, health care.
Both were/are determined to ram their issue through come what may, regardless of world or American opinion and regardless of its political consequences.
Both started/wants to start a huge undertaking with only a vaguest notion of whether it would/will work out.
A difference? Bush was willing to spend billions while Obama wants to spend trillions.