Good fictional leagues can indeed be hard to find, but when you hit on one it's a true joy to experience. In addition to the fine options listed above, I'd encourage you to take a look at the
Planetary Extreme Baseball Alliance (PEBA). The owners in our 24-team league work tirelessly to build a believable fiction around the on-the-field action.
In a couple recent developments, for instance, we've seen a team
draft a recently-deceased player and witnessed a suspension and fine levied for a
clubhouse meltdown by a visiting manager (the suspension and fine were both actually enacted in-game). You can view some more choice selections of our owners' fictional output
in this thread, or you can browse our
news archive.
While we don't have any openings at the moment, we'd very much like to hear from people with a strong interest in fictional leagues. Participating in another fictional league is no barrier of entry; in fact I think it'd be great to see owners bring over some of what's happening in one of their fictional leagues to a new one. That kind of creative cross-pollination would be very exciting!