The alternatives to Obama were McCain in 2008 and Romney in 2012. No, Howard Dean was never going to be nominated let alone elected. The same is true for all the other Democrats who ran in the primaries with the possible exception of Hillary. She could have been nominated and may have been elected. But few Obama detractors hold her up as a paragon of liberalism.
So it is a choice. Elections are not about everyone's separate version of the perfect candidate against a schmuck. They are about the two people on the ballot. So if we had not elected Obama what could have expected to happen and not happen:
All of the Bush tax cuts would have been extended
More tax cuts for wealthy enacted
Estate tax repealed
No repeal of DADT, and walk away from DOMA
No Dodd-Frank (which Warren praises by the way)
Likely we'd be at war with Iran
Likely we'd be fighting in Syria
Maybe we went to war against Russia over Georgia (Remember we're all Georgians)
Legislative weakening of Voting Rights Act
Larger Defense Budgets
No unemployment insurance extensions - ever
Smaller budgets for SNAP, Housing assistance, job training, etc.
And the list goes on and on and on.
Sure people aren't happy. They forget how bad things were five years ago and see a recovery that's far too slow. They also don't hear any voices touting how far we've come. More importantly, they don't think about where we would be if McCain or Romney had been elected.
I'll take President Obama with any label you want to put next to him against the alternative any day of the week.