Probably 20-25 different rappers have put out three consecutive LPs that were better.
Nas - Stillmatic, Lost Tapes, God's Son / Illmatic, It Was Written, I Am
Jay-Z - Vol. 2, Vol. 3, Blueprint
Eric B. & Rakim - Paid In Full, Follow The Leader, Let The Rhythm Hit 'Em
Ice Cube - Amerikkka's Most Wanted, Death Certificate, The Predator
Mystikal - Mind of Mystikal, Unpredictable, Ghetto Fabulous
DMX - It's Dark & Hell Is Hot, Flesh of My Flesh, And Then There Was X
Wu-Tang Clan - 36 Chambers, Wu Forever, The W
Ghostface - Ironman, Supreme Clientele, Bulletproof Wallets
Etc., etc., etc.
I don't want to keep listing albums, but Outkast, Kanye West, Tribe Called Quest, EPMD, 2Pac, Redman, Mobb Deep, and on and on and on.