First off, you gotta have top notch production, cuz I can't feel an artist regardless of how talented he is, if his beats are lackin (for example-Canibus). But as far as the artist goes, just come with something original. Do the shit your way, put a different twist on shit. Start your own style that people are gonna wanna clone off you. Combine those two, and to me, you got a classic album. Just like:
NWA-Straight Outta Compton
Bone Thugs-N-Harmony-Creepin On Ah Come Up & E. 1999 Eternal
Twista-Adrenaline Rush
Snoop Doggy Dogg-Doggystyle
2Pac-Me Against The World
Nas-Illmatic & Stillmatic
Dr. Dre-The Chronic
UGK-Super Tight
Scarface-The Fix
Do Or Die-Picture This
Brotha Lynch Hung-Season Of Da Siccness