Did American's (sorry for the umbrella) expect him to be a miracle worker or something? The world's economy was a piece of shit when Obama became President. Given the task he had upon being sworn in, he was never going to be as amazing as everyone thought. There was WAAAAAY to much expectation and 'ZOMG OBAMA IS OUR SAVIOUR' coming through from the US. Anyone with their head on their shoulders could see that he was always going to be average at best. The results people wanted to see were far to unrealistic for what anyone could achieve in such a short space of time. 4 years is not enough time to turn around the general fucked upness of America's economy at the moment. And generally I think Obama has done an alright job with what he was given. Certainly not in anyway a bad job. There's always going to be people who will be rubbed up the wrong way by any decision.
It's the same reason everyone hates the lib dems and conservatives at the moment in Britain. Labour fucked everything up (as usual), and it's on the shoulders of the next party to fix it. Problem is, one term is not long enough to see significant results and now everyones pissed off because things weren't magically fixed with a change in leadership.
It's kind of bizarre to watch.
It's funny how you say Labour fucked everything up, when it was Thatcher who was destroying the foundations for a sound economy in the 80's and how both wings of the political spectrum have contributed to the insane amount of debt by conducting costly, pointless and fruitless wars and endorsing a flawed economic policy of boom and bust, making money from money instead of manufacturing while the bankers were buying up islands and the mega corps were dodging taxes.
The problem isn't with the flavours in the box, it's with the box itself.