Now we have Mir Hossan Mousavi, said to be a reformist, vs Ahmadinejad, a ideologist. There are another 2, Mehdi Karroubi and Mohsen Rezhaei, the ex IRGC chief, but these seem to be minor players.
From a Western and perhaps international standpoint, hopefully Mousavi or Karroubi wins and the ideologist rhetoric, belligerent stand and nuclear weaponeering will be reduced, and the economy will improve. As for China and Russia, its not immediately clear who they would support.
The problem is, nobody knows who is going to be elected, especially if the 2 major contenders, Ahmadinejad and Mousavi, have different power bases. Also, Mousavi and Karroubi don't exactly love the West either, as seen by their track record while in power.
The question of corruption also hangs over the election. With corruption being quite rampant in Iran, its not unlikely that someone's going to try to rig the election too.
Let's also not forget that the supreme leader, Al Khamanei isn't elected and isn't answerable to anyone.
So far, the international community has been shooting itself in the foot by using sanctions which affect everyone and not just the regime. This, in addition with historical hatred going back to colonisation and the Shah, means that Iranian attitudes towards the West may well be hostile.
Will international hopes then be justified that Iran's belligerent stance is going to decrease? Hard to say.