This may have been asked before, but didn't see it:

[clydefrand]

Why is Obama's rating so low when so much great stuff has happened under his watch? Is it the Repukes don't like the
fact that a black man could possibly do so much good and they just can't stand it?
L O N G L I V E O B A M A!

[underpants]

1. The media, the corporate media

They don't remind the public that the ARRA worked amongst other things.

[upaloopa]

2. People in this country do not take the time to think

critically about what the media says about Obama. The media is owned by those who want someone else as President. So they will not say positive things about Obama and the people will not hear it.

[liberal N proud]

3. Propaganda

All at the hands of several 3 letter organizations and those that feed into them.

FOX, CNN, NBC, ABC, CBS should I go on?

And that is just the propaganda for those too lazy to read.

[csziggy]

4. President Obama's approval ratings are really NOT all that low

Compared to many recent presidents' rating at this point in their time as president.
President.....Lowest..........date
Obama..........38%.......3 Sep 2014
GW Bush.......25%......31 Oct 2008
Clinton..........37%......27 May 1993
GHW Bush.....29%.......31 Jul 1992
Reagan.........35%.......28 Jan 1983
Carter...........28%.......29 Jun 1979

President Obama has the highest "low" approval rating of ANY president in the last 35 years. The media is framing it to make people believe that Obama and his policies are failures - when the American public does not truly believe that.

Wikipedia has a very complete chart of approval/disapproval highs and lows that will put a MUCH better perspective on presidential approval ratings than the MSM gives us: http://en.wikipedia.org/wiki/United_States_presidential_approval_rating#Historical_comparison

Here is another set of comparisons in chart form:
http://online.wsj.com/public/resources/documents/info-presapp0605-31.html

[Prophet 451]

5. A few reasons

In no particular order:
"scandals" - By which I mean that the right just makes shit up and, via their control of the media, gets it into the public mind.

Corporate-owned media. With the exception of three hours on MSNBC weekday evenings, all your media leans right to some degree.

Racism - Let's not lie. At least some of the insane hostility directed at Obama is because he's black.