They produce as much sulfur as all the cars in the world (because cars don't produce very much sulfur). For other types of pollution, cars produce much more.
As far as whacky comparisons go, I'd always wanted to do some back of the envelope calculation comparing smokers' CO2 output to cars'. Also, always wonder how much cigarette filters (that are supposed to capture various chemicals) that get thrown on the floor could contribute to (e.g.) water pollution, if at all.
It's a pretty easy calculation considering smoking is basically carbon neutral. Almost all the carbon in a cigarette was removed from the environment by the tobacco plant when it was growing and gets returned to the environment when smoked. At most, cigarettes redistribute carbon from the regions where they grow tobacco to the places where the cigarettes are smoked. If anything, cigarettes deposit a small percentage of its carbon into the lungs of smokers which, after the smoker dies and is buried, is essentially removed from the atmosphere.
However this is only the case for CO2...as you mentioned, cigarettes have a bunch of other nasty chemicals that become pollution when smoked.
