A lot of the people you named are more lyrically vicious than most rappers out today.
To answer you question.... or to address your opinion, the older breed of MCs deserve credit, if for nothing else, for inspiring today's rappers. Every rapper you see out today has rappers before them that gave them inspiration to do what they do.
If we didn't have Kool G Rap would we have a Raekwon, Ghostface, Nas, AZ, and the many others who rapped about drugs dealing and crime.
If you we didn't have Kane, would have rappers with swag and style? People talk about Jay-Z being the inventor of swag, but Kane was on that shit in 87.
Not to mention the amount of rappers today who are using the rhyme-schemes of Rakim, Kane, & G Rap.
If you didn't have an LL Cool J making songs for the ladies, would we have a Drake, Ja Rule, etc. who sell millions doing just that.
A lot of the rappers you named give credit to a lot of older MCs that you won't. Outkast gave props to Tribe & Run DMC. T.I. Gave props to Scarface & UGK & asked them for permission to be King Of The South.
KRS 1 was dissing niggaz as a gimmick before 50 Cent graduated from elementary school. Speaking of 50 he shouted out Rakim in a one of his songs.
The rappers you say are great are/were STANS of the rappers you say get too much credit. Styles have evolved some, but in a today's game rap is pretty much stagnant.
As far as which rappers are better, most rappers from the 80s give props to rappers from today. KRS 1 dedicated a song to Nas, and many old school rappers came together to make three posse cuts on Nas' "Where Are They Now" from HHID. KRS 1 said Wayne is the best rapper out right now.