Obama must have used a lot more drugs and committed crimes while doing so or sold them to others if he's comparing his drug use to those in prison. His current crimes against the country are probably more serious. Maybe that's what he really meant?
In the 1970s we used to visit men in the old Ohio Penitentiary in downtown Columbus --black, white, Christian, Muslim, young, old; murderers, thieves, organized crime and white collar--you name it, we met them and developed relationships. One charming young guy in for burglary and drugs had even pimped for his wife. I never met one who said he didn't do the crime, but they didn't like the time or the parole board because it was "unfair" that someone else did less, or got released early. Taking risks was an even bigger "high" than drugs. Nor were they crime free before what sent them to prison (except for "crimes of passion" which were usually one time) they were caught after many years of pulling it off.