To grasp the greater landscape of important jazz works, artists, and more importantly WHY they were/are important, I think you need a good sampling from each era. Some of the other posts have put you on to the '60's and contemporary music better than I probably could, but you shouldn't forget the jazz age musicians, because thats where it all started (if you want a lesson on how to craft a pop hit, you wouldn't skip the Beatles, would you?). I would start with a direct comparison of Bix Beiderbecke and Louis Armstrong, try Armstrong's Hot 5 and Hot 7 recordings, as well as volume 2 of the Bix Recordings (this encompasses most of the stuff from 1927-1929, before he joined Whiteman's Orchestra). I would also recommend Count Basie's Decca Recordings for a sampling of the original Kansas City Sound of the '30s, as well as Benny Goodman's Original Small Group Recordings, with Teddy Wilson, Gene Krupa, and Lionel Hampton. These musicians have no peers. Listen to some of Hampton's contributions to the Goodman small group and you will no longer why they kept wheeling this old guy up on stage at the bluenote well into his nineties.