Senator John McCain is already appeasing the neo-conservatives, so I don't think that's really an option, unless you really want war with Iran.
Senator Hillary Clinton lies out of every orifice, so you can bet those promises on Universal Health Care (now with corporate backing!) and pulling the troops out of Iraq are going to go up in smoke the moment she steps in that oval office.
Senator Barack Obama has a voting record that often trumps exactly what he talks about: change. If he was so against the Iraq War vote, where the heck was he? In all his interviews and his justifications, he rarely ever takes responsibility. At least Clinton has the stones to fess up to mistakes (then again, she's probably lying about her perception of it being a mistake anyways).
So now it's all up to just choosing the lesser of two/three evils. The same way it's been for so many years.
I second that vote for Arnold Schwarzenegger. Maybe he can go back in time and convince certain candidates at gunpoint not to run.