Every president is hated by the opposition party in the U.S.
Trust me millions of people hated George W. Bush, Bill Clinton, and so on. Historically after a new president is elected there is a "honeymoon period" and after that's over the opposition party dedicates itself to making sure that president is NOT re-elected and if that fails they attempt to heap various amounts of scandals and distractions during their second term to keep their party from winning a 3rd term. Right now the favorite is Hilary Clinton another Democrat.
More often than not the nation chooses to elect the opposition party after an 8 year run with the previous president's party. One of the few exceptions was with George H.W. Bush who succeeded president Reagan in 1988.
Having said that many people dislike a president for personal reasons as well. In Obama's case race is probably a factor in addition to his party's agenda. For some people just his existence sickens them. Even when he agrees with some Republican initiatives they'd rather stall or vote against it in order to not make him or his party look good. It's extreme gridlock in D.C.
A lot of folks dislike him but fail to acknowledge (if he left office today) VP Joe Biden would uphold Obamacare, pursue a raise in minimum wages, fight for immigration reform, and look for ways to revamp student loans and prop up the "middleclass".
Obama is not doing anything that the (Democrats) aren't in favor of! The people who hate him or any other president actually hates that president's (party agenda/platform). The president is a figurehead.
With regard to Obama and key performance indicators when compared to when he took office in 2009 during the "Great Recession" anyone who says things are worse now is living in denial! Unemployment has dropped from 10% to 5.9%, the stock market is at historic all time highs, foreclosures on homes have dropped significantly, home values are increasing, projected deficits are dropping as the wars come to a close, and Osama Bin Laden is dead.
Historically American's blame their misfortunes on whomever is in the White House at the time. However some people are actually personally doing BETTER than they were still may hate his policies!