Deary me. Cannot choose one.
I played double bass in a local symphony orchestra for several years, and I'll tell you, the fun ones to play aren't necessarily the fun ones to listen to. Mozart is a blast to play (because the bass is typically fairly easy and you can actually immerse yourself in the sound, which is so powerful up on the stage), but I haven't listened to any of my Mozart recordings for 10 years at least. Mahler is a bugger to play, but fairly entertaining to listen to. Same with Sibelius and Beethoven. Of course Beethoven had Domenico Dragonetti as a bass virtuoso to trouble all the rest of the bassists in the orchestra. And trouble them he (they both) did. Bass hasn't been the same since.
Bach is both, to be sure, along with Vivaldi. A tad antiseptic (you don't get infected barbed-wire lacerations listening to them), but also timeless and brilliantly constructed.
But my favorites to listen to are such as: Schoenberg, Berg, Webern, Szymanowski, Bartok, Penderecki, Stravinsky, and Janacek. To name a few. These may leave a few welts.
And yes: "never enough time" is spot on.