Ehhhh, that might be the origin of it, but the connotation is a bit different.
I agree with this entry in Urban Dictionary:
A "G" doesn't necessarily refer to a gangster. In Queens, among the individuals I'm acquainted with, a "G" is basically a person who has their "s*** together"....or someone who is good at life, all around. An individual who is good looking, in good shape, is intelligent, has money, is good with people, is with hot women, is well dressed etc. is a "G." Therefore, the majority of the hip-hop/gangster community are not G's at all due to their lack of brains, money, social skill, class, style etc.
Lil' Wayne is not a G (due to him not being successful in all facets of life, eg. inability to conduct himself appropriately, lack of intelligence etc.).
Jay-Z is a G (high quality lyricism, money, Beyonce, style, class etc.).
Sheesh. It is bad enough that someone has to resort to 140-character tweets to express their opinions. Then, when they write like this, that just about seals the deal. And before someone says it, I know I don't have to follow them, which is why I don't. Her, or anyone else, for that matter.x
Sorry for the grumpiness, but the whole concept of Twitter drives me nuts.