The term hip-hop as something that need to be made vehemently anomalous to the terms "rap" or "rap music" is ridiculous. Rap and hip-hop are %100 synonymous with each other. One is not made to describe the music, and the other to describe the "culture." "Hip-hop" is only a "culture" so far as urban clothing labels permit it to be. Although, its definitions are perpetuated and allowed to survive as long as they do because of self-conscious, defensive rappers and rap fans trying to legitimize rap as an art form, which is really unnecessary. There is a rap culture, no doubt, but hip-hop is not anything different and it is a ridiculous term.
Those said people trying to legitimize rap as an art form usually go about it the wrong way. They should be playing up the music, instruments (when applicable), studio production skills, and vocal talents. Something I see as an argument too often is that rap lyrics are "poetry." But, in most cases, the ones most being defended don't fit the bill of being poetic. I guess these rap fans never paid attention in English class. Poetry is often defined to be undefinable, but something it is most often agreed to not be is a linear arrangement of complete sentences directly outlining a series of events or one's thoughts. That won't even qualify you as free verse. A classical definition of poetry is, "The right word in the right place, in as few words as possible."
I've never made the argument of rapping to be just talking fast (or mumbling slowly in some cases...50 Cent, Mase, Puff Daddy), but there are plenty of times where I've thought that what their lyrics come down to is them just talking. Using "street language" and slang is not inherently poetic. Those are more related to a dialect, which is a style of speech before it is a type of poetic diction. There are definitely poetic rappers out there, but being poetic (i.e., abstract and esoteric) is also not a mainline to being good or exempt from critique.
Rap is the same as most any other music genre. It is indeed an art form, it does require talent, and there are only two kinds: the good kind and the bad kind.