whats the most important rap group of all time

[Elkoizm]

NWA.

Run-DMC set the blueprint (along with Juice Crew, Grandmaster Flash & The Furious Five etc - better known as the Golden Era of Hip-hop), but NWA was the one that touched a bigger fanbase and resulted in the spawn of actual 'rap', not hip-hop.

what's the difference between rap and hip hop as a genre? 

To me personally, the difference is a thin line between the two.

Hip-hop makes me think of everything before the early 1990's (and alot of the underground stuff post that era). It differs in the way that it's expressed and the way it's used as a term whether talking about a lifestyle or way of describing something.

Rap covers a range of styles of music but beginning with east coast rap, gangster rap, southern music and whatnot.
Rap is heavily focused on the spoken word that usually delves into a particular matter or subject (or even nothing!).

I struggle to find a song that's out today and say 'That's Hip-hop'. Unless it's underground and the song doesn't need a type of radio appeal to it.

Again, that's just my thoughts.

[TT Makaveli]

Wu...cause you know Wu Tang Clan is nothing to fukk with 

and 2nd NWA...cause i love gangsta rap and these guys were the pioneers of that!

[Darkwing Duck (The Reincarnation)]

Run-DMC set the blueprint (along with Juice Crew, Grandmaster Flash & The Furious Five etc - better known as the Golden Era of Hip-hop), but NWA was the one that touched a bigger fanbase and resulted in the spawn of actual 'rap', not hip-hop.
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Rakim