Gallup's Frank Newport says it's bad:

Bush's approval is lower than that of any president since World War II, with the exceptions of Jimmy Carter (who had a low point of 28% in 1979), and Richard Nixon and Harry Truman, who suffered ratings in the low- to mid-20% range in the last years of their administrations.

That does sound bad, and 28 percent is certainly nothing to brag about, but lower than any president since World War II? Well, as he says, Truman, Nixon, and Carter all had lower ratings. Add Bush and that's four presidents since World War II who've had ratings equal to or lower than this. We've only had ten presidents since World War II. So, by my reckoning, Bush is right in the meaty part of the curve.