Nothing really, but is not like US presidents do something good for the World.

Pretty much... absolutely nothing. Yet the joker still won the nobel peace prize a few years back, that still boggles my mind.

Rofl, watching right wing and left wing Americans argue in circles with each other on television and on radio is bad enough. Now I get to see people doing it on a gaming forum using regurgitated rhetoric they heard from their favourite talking heads on Fox or CNN.

Not really sure why they even argue at this point. No one is willing to change their "opinion" even based on facts. If you're on the right then the left is always wrong, and vice versa. End of story.

http://whatthefuckhasobamadonesofar.com/

Conveniently there is a website that explains just what you're asking for.

Bush saved millions upon millions of African lives, as well as creating the largest marine preserve 

Hah, jokes on you! No one watches CNN!

On topic: I honestly can't think of anything 

by "world" do you mean the USA???

Nothing except not been a Republican.

I used to watch CNN ...

CNN has (essentially) committed suicide in the past 12 to 18 months. They spent a couple decades building a brand based on unbiased quality journalism and, while they did have issues with bias, they mostly remained non-partisan; at least compared to MSNBC and Fox. Over the past couple of years a large portion of experienced employees (who generally hid or balanced their biases) have left CNN and been replaced by a bunch of partisan hacks.

Since a large portion of CNN's userbase were people who got their news from multiple sources and were looking for professional and unbiased news from CNN, their massive partisan shift alienated most of their userbase.

You can only half-blame them. It's like when Cartoon Network tried a move towards live-action programming because they're a perpetual also-ran against Nickelodeon and Disney. It's the pressures of being or being owned by a publicly traded company. Actually, same company, now that i think of it...

Not a huge amount. But then he is the president of the USA, not of the world.