"I would agree with your argument if your President had real power, but his power is limited."
True, but consider what the situation would be like if Romney had been elected. He'd have almost free reign. He'd be appointing the next few Supreme Court justices - which is insanely important.
We could pretty much immediately write off healthcare reform, rip huge chunks out of social spending, and probably throw a bunch of whatever gets saved back at the wealthy and at the defense industry.
Put another way, imagine what would have happened if Gore had been elected (err, well... if he'd taken office, let's put it that way) in 2000 instead of Bush: Do you think Gore would have ended up invading Iraq, promoting loose monetary policy, giving insane tax cuts to the wealthy? I doubt it.
So, yeah, Obama hasn't got the power to *undo all the damage* that's been done, or to fix every problem that exists. But Romney would have had an incredible ability to do *more* damage. That in itself makes Obama being elected meaningful even if he just sat around doing nothing. Which, by the way, he hasn't - he's actually accomplished quite a bit, and suggesting otherwise by trotting out a list of obnoxious-but-relatively-insignificant-in-the-scheme-of-things pet causes like Guantanamo is disingenuous. Part of Obama's problem is that he *has* focused on getting things done and on prioritizing, which has meant more real progress in the long term but fewer feather-in-cap type bullet points. I'm fine with that.
And I'm sure as hell glad we don't have to find out the hard way that Romney isn't the same as Obama, the same way we found out that Bush was most definitely not the same as Gore would have been.