Rolling with gangsta-sonic hitmaker Dr. Dre may have made antiheroes of Snoop and Eminem, but gruff-voiced Xzibit is still seeking his place. Man vs. Machine, his fourth album (second under Dre's umbrella), finds him trying on the thinking-man's-thug role -- with moderate success. (See ''Release Date,'' the clever prison-as-metaphor opener.) Ultimately, though, Xzibit's best efforts are done in by the usual culprits -- misogyny, crudity, and blinding bravado. Rather than stand out, he merely fits right in.