I feel like his music was never as lyrical as his 90s counterparts, and his songs imo feel a bit stale and samey after a while. Because of this, I think his music has aged pretty poorly, especially compared to otehr 90s rappers like biggie that have aged great. However, i do believe that he is the most influential rapper ever
Nice to se MF Doom getting a mention here. I'd also add Dr. Octagon, Dr. Dooom and Buck 65 as underrated (at least, not very well known). Possibly A Tribe Called Quest - they might be more famous but I still think deserve to be higher up the exposure/hype chart. Don't know if you'd include Beck, but a lot of his vocals are rap rather than singing; I've never heard him mentioned among rappers, so perhaps.
Underrated: Earl Swatshirt, Domo Genesis, JPEGMAFIA, Black Thought, MF DOOM
It's possible to be good and overrated.
Kendrick Lamar is good and overrated, IMO.
Underrated: NF, Connor Price, Tedashii, Twenty One Pilots (they don't always rap but when do it's 🔥🔥)