The bass plays the same 12 notes that all of the other instruments play. (Except I manage to find a few more in-between on the fretless

). Whether a bass solo, or any instrumental solo for that matter, is good, in my opinion depends on whether it fits with the song it's in and tells a good story.
If I heard a singer stand up and scream "blah-ga-blah-ga-blah-ga-doo-blah-ga", or some such, as fast and loud as he or she could, I wouldn't like it, even if it were technically hard to do. On the other hand, a catchy melody and clever words are priceless even if simple. Ask Aimee Mann - both keep her career going year after year.
One mistake I see bass players make is trying to fit every technical soloing gimmick they have into the one solo they might get per set, or per night. These guys aren't considering the context of what they are playing - what the song sounds like, the feel, what the soloists that came before did, etc. By making a solo "relevant", it becomes much more pleasing, and it seems to belong in the song.
One way to get yourself halfway there is to key off of the melody of the song for the first few bars of your solo. Listen to Trane - he did that 75% of the time. It gives you, and the audience, a sort of "thesis" for your solo, and gives you something to build on. You may find you are playing fewer, but better-chosen, notes this way and not simply noodling on scales.
All that said, a lock-tight groove is just as interesting to me. Check out Tom Kennedy on Dave Weckl's "Transition" for some great groove work.
And how did Stefan Lassard get that gig, anyway?