LL has it right- Iran is a politically diverse nation, much like the US. Ahmadinejad is the Iranian equivalent of GWB, a hard liner, but lacking real power. His position is a lot more ceremonial that being president of the US.
He was elected in response to the whole axis of evil routine from the Bush Admin, somebody who'd stand up to America, stand up for Iran, and he has.
And the remark wrt failure of our policy towards Iran is really quite true- we've allowed their government no legitimacy whatsoever for 30 years, yet they're still there, and show no signs of going away anytime RSN. Failure is as failure does. If we want things to be different, then we have to make the first move, which Obama has done.
The more our govt raves about teh ebil Eyeraynyuns, the more they'll feel threatened, the more they'll support their own hardliners. Unlike the Bush Admin, the Iranian hardliners don't have to puff up the threats they face- The military might and economic hegemony of the US, particularly under the Bush Admin, has been a very real threat to them. From their perspective, it doesn't help that we refuse to muzzle our nasty little attack dog in the region, Israel.
Possibilities for rapproachment, as was done with the Soviets and the Chinese, are quite real, and have been for many years. We've simply refused to engage in them. That's the kind of policy change required, and what the Iranians are talking about. Like it or not, their govt is legitimate, and has the support of the populace, particularly when it comes to rejecting foreign interference in their affairs. The only regime change they'll accept is of the internal kind, and the only way we might see what we want is to back off and let them determine their own destiny.