Bush:
Invasion of Iraq - While popular at the time, looks hardly justifiable with the passage of years. Rode the momentum of Afghanistan to seize the initiative to "finish the job" in Iraq. Delivering democracy to countries you know nothing about is a tall task. Extremely costly in every sense.
Consolidating power and Growing the federal government - too numerous to list.
Pumping home ownership - Bush played his role in ramping up the housing bubble.
Obama:
Iraq/Afghanistan - Escalation of Bush's folly followed by total bail out according to arbitrary dates.
Divisiveness - Politics is often divisive, but not typically so from the seat of the president. Constantly playing the blame game, blame republicans, blame corporate america, blame wall street, fair share, get in the back seat, etc.
Obamacare - Cluster !@#$. Delivered "free healthcare" to the States at the worst possible time. See the next note.
Economic Recovery - Jobs Bills 1 through 10,000, lowest labor force participation rate since the depression, stagnant growth 6 years later. Crammed his namesake legislation down the country's throat creating loads of economic uncertainty while the country was still attempting to crawl out of the recession.
Spend, spend and spend - Followed Bush's lead and decided to double up.