Tbh on average the typical beat makers from the 90s simply didn't know anything about Bebop scales or Altered scales, syncopation and polyrhythms, shifting keys several times throughout a song, writing charts for several instruments or other more complex musical ideas...we did have some rappers/producers that tried to introduce these ideas (Chronic, Outkast albums,...) but it really doesn't mean shyt if you can't do it right. Thats why lllmatic is probably the only rap album from the 90s that get ranked high on these respected all time lists (in any musical genre). That album was just perfect. It benefits from the fact it was simple and more basic from a musical standpoint, but at least the shyt Nas did, he did it right. Other than him, you basically have to check more modern hip hop artists if you wanna see rap albums getting heavy praise in the music world...thats where you find Kendrick Lamar, Kanye West,...
My top 5 all time? I'd have a list for my best albums, and one for my "favorite albums"
To Pimp A Butterfly - Kendrick Lamar
Kid A - Radiohead
Wish You Were Here - Pink Floyd
Abbey Road - The Beatles
Ok Computer - Radiohead
On my favorite albums list, I'd probably replace Pink Floyd & The Beatles with Nina Simone and Prince.