If we're talking a nuclear Iran you're right.
If we're talking an Iran backed by Russia, highly likely, then again you're right.
If your talking Iran with a coalition of other Arab nations, very possible, Syria, Jordan, Lebanon and maybe a few others, you're right.
If your talking a conventional armed Iran, by itself, with Iran attacking Israel, in an all out attack, I'd say the war lasts 3 days, maybe 1 week, with Iran not faring well.
The problem is the afterward. Iran is one of the largest players in the world oil market. The after effects globally would be huge. Add to that the alliance with Russia, and its oil and natural gas resources, Russia wouldn't sit idly by as Iran got its buttox kicked.
If Iran were sure of its conventional military, Ahmanutjob would be doing more than just rhetoric.
Iran fought Sadaam to a standstill for the better part of a decade.And the fact that it would be Israel they'd be fighting this time would,I'll wager,stiffen their resolve tenfold and I'll wager that they'd be far better armed than they were then.