Listen: I like rap that has meaningful lyrics. I would completely agree with anybody when they say Lil Jon, Ying Yang Twins, etc. suck. Go listen to some Tupac, Proof, or Obie Trice if you want real music. There are plenty of others, but these are the only ones that come to mind right now.
Word. I like Lil' Jon and the Eastside Boys, etc.. but not for their lyrics, the best rap is done as you suggested; Tupac is a prime example, Tupac's "Changes";
It's time for us as a people to start makin' some changes.
Let's change the way we eat, let's change the way we live
and let's change the way we treat each other.
I see no changes all I see is racist faces
misplaced hate makes disgrace to races
We under I wonder what it takes to make this
one better place, let's erase the wasted
Take the evil out the people they'll be acting right
'cause both black and white is smokin' crack tonight
and only time we chill is when we kill each other
it takes skill to be real, time to heal each other
The end.