Great. That headline is also rather meaningless and dishonest
1) Comparing FAVORABILITY ratings to JOB APPROVAL ratings is comparing apples to oranges and is rather intellectually dishonest. They are in essence, two very different things. Favorability rating is basically, "Do you like a guy." Job approval rating is "Do you approve of the job someone is doing." Those are two very different measures of "popularity."
2) Almost all ex-Presidents enjoy growth in their favorability ratings after they leave office. They don't have to deal with the media, Congress, the realities of governing and executing policy, scandals that may or may not be their fault, etc. All ex-Presidents have to do is stay home, make intermittent public appearances, not put themselves in a position to do something douchebaggy that will be reported by TMZ, and they'll be fine. Look at Jimmy Carter.
3) A better comparison would be to compare Bush and Obama's job approval ratings at the same point in their respective presidencies. Obama's current approval rating is about 47% based on Gallup. Bush, at a similar point in his Presidency, was in the low thirties.
But I suppose it's easier to grab on to a partisan bull**** headline and not do the intellectual legwork to notice that apples are being compared to oranges than it is to be honest about reality.