LL dominated the second half of the 80s when I was in high school. He dropped his first album in late 1985 when Rap albums weren't that common. Radio rocked all the way into 1986. Then he dropped Bigger & Deffer which was a 5 mic classic. He had a battle with Kool Moe Dee, Ice T, Hammer and a handful of lesser known rappers.
LL didn't just have a three year run like Run DMC, DMX, 50 Cent or Dipset, he continued to drop heat well into the 90s. I Shot Ya (Remix) and 4,3,2,1 had LL rhyming with rookies and he still shined.
He even had some success in the early 00s.
The only reason he's not the all-time GOAT is because he was never really my favorite MC. I thought Rakim and KRS were better in the late 80s, although LL shined in the spotlight longer.
I voted top 10
Run-DMC had a longer run than 3 years.