I could probably give 100's, here's a quick 5...
1: He has many incredible elite level classic songs, songs like Dear Mama, Keep Ya Head Up, Unconditional Love are some of Hip Hop's/music's greatest songs. When you really look at all of his GREAT songs it's amazing.
2: He was a great songwriter and lyricist, he was POTENT with his lyricism and delivery, his shyt could HIT you in a very powerful way cause of his artistry.
3: His subject matter was extremely diverse, he touched on so many topics, the hood shyt, to relationships, clubs, family, extremely personal shyt, paranoia, everything.
4: He had 1 of, if not the GOAT Hip Hop voice.
5: He utilized so much flavour in his songs, he was entertaining to listen to, if you really pay attention to all the flavour and inflections he put in it's remarkable.
Bonus:
6: He was a poetic writer, he put himself in numerous perspectives articulated and articulated that from first person and even as a narrator too.
7: He was a student of the game, so he studied rappers like KRS, Scarface, Cube and so on and incorporated some of their elements into his style to create an amazing blend.
8: He poured his heart into his music and wasn't afraid of getting extremely personal or vulnerable, he was real with his music.
9: In his short time being alive he made 4 classics, high calibre work at that, had a phenomenal run and even had great music released long after his death.
10: He had compassion in his heart and it translated to his music, he was trying to connect with people and give game through his music, his music is valuable and timeless because of the game and jewels it is littered with. He is immortal, he will always be remembered and loved because of how deeply he touched and influenced people.