If someone who currently listens to Rock or R&B asked for something Jazzy they might like, I would probably recommend some "tweener" stuff like:
-Steely Dan "Aja" "Royal Scam" "Goucho"
-Chicago "at Carnegie Hall"
-Stanley Clarke "If this Bass Could Only Talk" "Hideaway"
-BB King/Diane Schuur "Heart to Heart"
-Concord SACD Jazz Sampler
-Spyro Gyra "Catching the Sun"

(I would not recommend Kenny G, Micheal Bolton or other soft/light/new age stuff. My apologies to any who like this style- but I wouldn't want to be responsible for leading someone down this particular road of Jazz.)

As far as a few of the most essential Jazz recordings from my Jazz collection:
-Manhattan Jazz Quintet (First Album, 1984)
-Stan Getz/Charlie Byrd "Jazz Samba"
-Miles Davis "Some Day My Prince Will Come" "Sketches of Spain"
-Toots Theilman "Brazil Project"
-Stanley Clarke "Journey to Love"
-Joe Pass "My Song"
-George Benson "White Rabbit"
-Chick Corea "My Spanish Castle"

Of course, these are mostly "somewhat modern" Jazz selections and I do appreciate the Latin influence.

As one builds their Jazz collection, I think a "starter kit" for each Jazz era could quickly follow.

I wish I could discover these for the first time again, however, they do continue to delight.

Enjoy!