To call either of them anything close to GOAT is absurd imo. Both of them are considered GOATS because they were killed at the height of their careers. One can actually argue that pac was headed for a downward spiral, with his whole makaveli and killuminati and dre dissing shit in his last year. And biggie was definitely leaning way more mainstream and he seemed like he would've been all radio singles with one more album release.
Pac:
-fans use his message to compensate for his average lyricism, despite his "message" being just as much violence and money and bitches as every other rapper
-every release of his was only above average until death row and dre beats really made him look better
-lacks complexity and innovation, same ol 1-2-1-2 rhyme structure that dates back to grandmaster flash and kurtis blow, he just did it faster with more voice emphasis
Big:
-next to no depth at all, as simple a subject matter as you can get, lots of rags to riches, brand name bragging, guns/weed/pop the bubbly, women, coogi, etc.
-considering his era he was definitely one of the innovators of complex rhyme structure, but his delivery was often monotone and lacked punch(gimme the loot aside)
-the better lyricist of the 2, but he and puffy could not put together a quality song the way pac and dre could.
And I actually like both of them a lot, I just think if you don't consider their deaths then they aren't sniffing the top 5
