It seems like the evidence is pretty strong (although not beyond any doubt) that the election results were tampered with to inflate the Ahmadinejad totals. It is however nowhere near as clear that Ahmadinejad didn't actually win. It may well be that even if the results hadn't been cooked, he would have still won, just by a much narrower margin. Or maybe he lost. My expectation at this point is that this is actually now a completely unknowable question. The relevant evidence that would be needed to decide such a thing is probably long gone.
At this point the events in Iran have moved beyond the just this particular election and the results thereof. Who will actually be Iran's President over the next few years... and who will be in charge in a broader sense, will be determined by many things... but who got the most votes last week is no longer one of those things.