Cannabis should not be classified at all as an illegal drug. It should have the same prohibitions as alcohol or tobacco. Remove all the silly taxes, though. Smokes should be $2-a-pack and be advertised with cartoon camels.
Opiates and methamphetamine should be prison for use and possession and death for trafficking. That would include doctors and pharma companies that over prescribe painkillers. A special task force/death squad should be assembled to shoot all tweakers on sight.
Cocaine should be semi-legal, so long as it is used only with booze, the way god intended.
Psychedelics should remain illegal, but with a silent code of non-enforcement.
Designer drugs like ecstasy are a grey area, although the club music that often accompanies their use should be dealt with in a draconian manner.