Obama somehow couldn't reverse the Bush tax cuts in four years but he could push through unpopular programs like Obamacare, the Stimulus Package and the Bank Bailout.
Obama didn't do the Bank Bailout. Bush did. It's disturbing how many Americans can't seem to get this fact straight, but a lot of people (the GOP/Fox News etc) would prefer that they didn't. Obama didn't reverse the Bush tax cuts because they were going to reverse themselves in 2010, and he wanted as much stimulus as he could get to keep us from falling into a depression after the financial crisis. In fact, he agreed to a two year extension for that reason, which is why they are expiring at the end of 2012.