Humans are good, but so are aliens... it all depends on how well they are designed to mesh. We rather like it if in a universe with many species that have populations equal to og greater than that of humans for the important characters to be at most a similar distribution across the species. Not a decisively larger human quota than alien. if the aliens are well-made enough, then humans are optional.
At the same time, pure human universes can also work well, though that requires more complex personalities and events to give equal depth.