The Lancet recently had an article assessing the harm of illegal drugs. While they’re not directly comparable by virtue of being legal, tobacco and alcohol were on the list.
Not surprisingly, pot and a host of other drugs (anabolic steroids, LSD, ecstasy, and khat) seem to be less harmful than alcohol or tobacco. I don’t drink alcohol, smoke, or take drugs (I’m a very boring person in that regard), but I’ve always thought the choice of what is legal and what is illegal is very, very odd.
FWIW, in my opinion a lot of drugs should be legalized.