Apart from sales to children, drugs should be perfectly legal.
The main reason is that what individuals do with their own bodies and health is their OWN business -- not the government's, not society's, not anyone else's. And since when is prison better for your health than drug use? Also, putting "the good of society" above the rights of the individual is a hallmark of socialism.
In any case, the Drug War will fail for the same reasons that alcohol Prohibition failed. It's all tied to very basic economics. Why is it that Americans can never learn from history?
If I were a drug dealer who was getting rich off selling drugs, my worst nightmare would be legalization! That would put me out of business, or at least take away all my profits. As for getting busted, the profits make it well worth the risk. (The only reason I don't deal drugs myself is because my conscience won't let me. If I had no conscience, that would certainly be my line of work.)
The more strictly drug laws are enforced, the more profitable they are to sell, and the more incentive there is for people to take the legal risks of smuggling and dealing/pushing them. That's right -- every single raid, and every single dealer busted, eventually encourages more drug dealers to take their place.
Of course, drug dealers are going to fight each other over the huge black market drug profits. That's what the gangsters did in Capone's time. How many people kill each other over alcohol today? Didn't the US murder rate drop by something like 50% after Prohibition ended? Still, the gang warfare associated with all those Prohibition gangster murders led to the 1934 NFA. Today, the gang warfare associated with drug prohibition is a major source of gun crime and is the driving force behind the push for more gun control and other violations of our civil liberties.
Besides, if people want to get high, then they'll get high, and there's nothing any of the Puritanical busybodies can do about it. If all illegal drugs disappeared forever from the face of the earth tomorrow, some people would simply start huffing glue or solvents, which is highly addictive and far more harmful than most (maybe all) illegal drugs. (Drugs like pot are even less harmful and addictive than alcohol.)
Sometimes I think the government knows all of the above. It's really not rocket science, so how could they possibly be unaware of the numerous parallels between alcohol prohibition and drug prohibition? Maybe they just want to continue the Drug War because it provides them with another excuse to crack down on citizens' rights.