If he wasn't being taken seriously by his neighbors, you'd have something to stand on on that argument. But that isn't the case. He is being taken extremely seriously. He's the President of Iran, a position with real power. He is not a mere figurehead by any means.
As for what you said about leader as a word to use. What would you use then? A leader is a leader. Terms like President, Chancellor, Prime Minister are just the titles of the position a leader of a nation has.
Okay, I'm going to put it straight now because you asked for it. Being American, you tend to read "president" anywhere as an office with the same very full powers as the U.S. presidential office, or close to those powers. That's rather misleading: president
tends to be an office the holder of which performs representative duties
, and not key policy making. The chief of state, in many countries, especially parliamentary states (those where the cabinet communicates directly with the parliament rather than with the chief of state, the monarch or president, and normally needs a majority to rely on in the legislative chamber of parliament) isn't the actual architect of policies or laws, sometimes they don't even belong to the same party as the prime minister. Even if they personally sign some laws they don't have much to do with formulating them or driving them through. Most of the time, even the power to *sign* laws is delegated, loaned out to the prime minister and the government.
The president of Iran has nothing like the power of a U.S. or French president or a British PM and the guys who actually call the shots are not close to him. I have already admitted it's unusual to have a president who makes that brand of strong statements, when he is not really holding the reins of power, but the reason I think is in what Marissa was on to. Iran has been surrounded by enemies ever since 1979, they can see that most of the neighbours are preying on them and that some of those nations have been or could soon be at war with them - openly or undercover. They know, too, that some of those war conditions have been fostered by greater powers behind the scene: the USA backed Iraq in the deadly war against Iran in the 1980s, the Soviet Union upheld a puppet regime in Afghanistan during the same decade. Afghanistan and Pakistan today are half-puppet republics of the USA and the frequent drone flights of the US are frankly a serious breach of sovereignty against these allies. It's not that hard to understand they feel surrounded and this is not a question of propaganda, it's enough to look at a map and research some about the countries in the region and their history in the last forty years to get why Iran feels there is need for loud and powerful action (though generally not by means of war) to avoid being pulled under by Uncle Sam and company.
So any regime in Iran that wanted to keep the country together, not just the present regime, would be compelled to make strong statements sometimes to avoid being attacked, or becoming a puppet of Russia or the USA: That's essentially what Ahmadinejad does. Sure, he does it in a distasteful way sometimes but it's not as if he's being taken 100% at face value by the neighbouring countries.
Leadership doesn't look the same, or function the same way, in all states, not even in all democracies. That's why leader
for the political "top exec" of a country is an unsatisfying and dumbing down word.