I agree with Matt that American Gangster was good but not great, but the question of glamorizing criminals is an interesting one. I initially had the same gut reaction to the movie, and found the 30-second cameo of a few nameless heroin addicts lacking after most of the movie was devoted to the high style of the gangsters. The women cutting and bagging the product seemed to be having fun, when the reality is that the work conditions in reality weren't so great.
But let's take a step back here. The movie depicted the cops as corrupt. Even though what Frank Lucas did was certainly bad, it's not as if the cops that were supposed to be keeping order were any better. They were racist and corrupt. Lewis emerged at at time when black men couldn't make it to the top of the legitimate world, so making it to the top of the criminal world was something. It's easy to discount people because they're criminals, but you also have to look at the opportunities in the legitimate world. If there's nothing offered there, of course the criminal option seems better.