The scope of his influence is probably better represented by the best homage rap artists can give anyone: being sample
d. Off the top of my head, he's been sampled in:
1992's "Jussamen" by Das Efx. The title stems from a sample of Slick Rick rapping "We're just some men that's on the mic," from La Di Da Di.
1992's "Blow Your Mind (Remix)" by Redman. The beginning of the song has a vocal loop of "Ah Ah On" from The Show.
1998's "We Like To Party" by the Vengaboys. The title vocal is sampled from La Di Da Di. When someone from the other side of the planet doing a different genre samples rap, that's gotta be a testament to its influence.
Snoop Doggy Dog also did a semi-cover in his Lodi Dodi (of La Di Da Di).
In 1999, he released an album, The Art of Storytelling which received good reviews but did not do as well in sales.