I like Huntsman a lot, but he'd never win his party's nomination in the current GOP climate.
I think Jeb Bush would have a reasonable chance...I don't think the "name" is destroyed, and even George W. Bush himself is going to be remembered better going forward than he was as his presidency drew to a close. In today's hyper-partisan political environment, there's roughly 45% of the vote you're simply not going to get no matter who you are and 45% of the vote you're going to get just by being part of one of the two major political parties. I think the Bush name is only beyond repair in the 45% of the vote who wouldn't vote for a Republican anyway.
I think Marco Rubio is probably their best bet for 2016, though. He's young, charismatic and, with a Latino background, has appeal beyond the older, white male demographic that's been boxing in the GOP the past two election cycles. His views are probably about as extreme as Paul Ryan's, but he's better at coming across as a moderate, without it seeming fake.
For the Democratic party, I think Hillary Clinton is their best candidate, if she's interested in running again, 8 years after her last attempt. She's quite popular, especially among the Democratic base, and she, like Bill Clinton, is the type of extremely pragmatic moderate who tends to do well in general elections. If she doesn't run, I'm not well enough versed in the Democrats' bench to know their next best candidate might be.