DEBATE - BEST RAP GROUP OF ALL TIME

I love the old school... I grew up in the Hip Hop Golden Era... when Groups Like NWA, Public Enemy, Outkast, Goodie Mob, Wu Tang Clan, Das Efx, Tribe Called Quest, etc dominated the musical landscape for me. I loved all of those groups back then for different reasons.. so recently on Facebook I asked the question... Who is the greatest Rap "Duo" key word duo because I did get alot of answers like Wu Tang and other great Rap Group answers... so I decided to expand the question... so in the blogs comments... leave your opinion... who is the greatest Hip Hop group of all time... and tell me why!!! Your opinion shouldnt count for shit if you cant even back it up with some logic or reasoning!! LOL this is supposed to be fun so please no hating on the opinions of Others