No doubt. Nas could rap circles around 50 even if 50 was possessed by the ghost of Tupac.
Album sales mean nothing. If 50 were daring to rap about anything other than hos and money he wouldn't get half the radio airtime he does, causing his record sales to flop. He is more commercially successful because commercial America does NOT want your average teenager hearing the sort of forward thinking and socially conscious crap Nas, Mos Def and etc rap about.