The sanctions on Iran are no where near as effective as the sanctions they had on Saddam's Iraq so I don't think he would be unpopular for that reason. Ahmedinejad seems to be very popular within the Arab world (from what I can see) but I don't know about the Iranian public. If you can remmember the Iranians rallying outside the British embassy in Tehran (I actually think some one let off a bomb but no one got hurt) when they captured the British sailors, the protestors were saying that the Brits shouldn't be returned and that Iran should be continue to be defaint to the west. I remmember one man from the protestors saying Ahmedinejad was the only remaining "hero" of the Muslim world. I don't think the sanctions on Iran are that evasive and I don't think the public notices the sanctions' effects on their lives (from what I see). So far Russia has saved Iran from more effective sanctions. If he's unpopular within the Iranian public it would stem from the public's fear of becoming a second Iraq.The sanctions that are in place have taken a toll on Iran and he doesn't seem to have very much domestic (popular) support; as the pressure has increased his support will decline within Iran (Our thinking... IMO). I believe this is our final attempt to "push" him over the edge. Perhaps, it happens from within or maybe an offer that Assad "can't refuse" is made (he has similar pressure already) will pull Syria away from Ahmadinejad.
I also think westeren media tries to make him look more unpopular than he is. IMO.