Most popular pet species?

[Firekracker]

I am relatively new to the site and have gotten somewhat into trading so I would like to know which species are the most desired/popular for future reference.

I'm not referring to specific older pets like the Elderwind, I am referring to species itself.

An input is greatly appreciated! Thanks!

[Sphye]

Hello, Firekracker!~

Ancients tend to be popular for their unique linearts and novelty. Bazaar-exclusive or event-exclusive species, like Glassworks and Foo Dogs, tend to be fairly popular, as well. Phoenixes are rarely released, putting them in a similar category to Bazaar and event exclusive species.
Other than that, which species are most popular tends to vary from person to person. There's not really a general consensus of species with the most demand unless their releases are less frequent.