So my good friend Narwhaler had taken the liberty of making a tier list to rank the PZ animals based on how well they look compared to each other. So with his permission, I decided to make a forum post around it with my own commentary
Now here's what each category means. See where your favorite animal has landed
Watermark + bintuwrong: Tiermaker has that dumb watermark and the old binturong is still a certified Frontier moment. I'd love to know how Frontier had a good one ready
Best quality: These are the best of the best. You'll notice that a lot more of the recent animals are here than older ones, with the ring tailed lemur being the only base game species. This is because, IMHO, Frontier has significantly improved their workflow, resulting in animals that are far better in most regards. I think the best showcase of this is to compare the Nile lechwe to the other antelope in the game, especially the ones lower on the list, or the water buffalo to the African buffalo
Great, minor tweaks: These are animals that are still great but with a few flaws that keep them from working their way into the premier echelon. For example, the red crowned crane is gorgeous but has some pretty awkward clipping when resting, a likely leftover from it being based on the flamingo. Even the Southern white rhino has somewhat stumpy legs (tho I think that depends on what specimens Frontier was using for reference) and the babies are small for the model (toddler model the size of a newborn). However, not bad overall.
They're ok, still improvable: These ones aren't TERRIBLE, but they could really, really, REALLY use some QoL updates, with the most common issue being very low quality textures when compared to modern cohorts. For example, compare the African savanna elephant and Indian rhinoceros to the later Southern white rhinoceros. The difference in texture quality is night and day. You also have issues of size (the hippo is FAR too big), texture (the great apes especially) and the rigs (The elephant rig has knees too low and the orangutan is far too similar to the gorilla). You also have a lot of cases where Frontier has made a very similar animal but just 10x better such as the water buffalo excelling over the African buffalo
Outright bad for various reasons: These animals have significant flaws that decrease their appeal. Examples include weird quirks with the rig (Formosan Black Bear never shutting its mouth and being overall quite glitchy), poor model quality (Plains zebra and the hyena), poor texture quality (the two birds), etc.
Sin: These are the worst of the worst. A combination of poor models, textures, and especially rigs that make these animals unusable without remaster mods. A lot of these are pretty obvious. The lion is universally considered far too cartoony for the slightly enhanced realistic style Frontier is going for, the snow leopard has the same issues, and the fact that the Malayan tapir hasn't received some form of QoL update is a real kick in the dishpan (Hoo hoo hoo).
If you want me to explain what I think of certain animals, let me know with a reply.

Now here's what each category means. See where your favorite animal has landed
Watermark + bintuwrong: Tiermaker has that dumb watermark and the old binturong is still a certified Frontier moment. I'd love to know how Frontier had a good one ready
Best quality: These are the best of the best. You'll notice that a lot more of the recent animals are here than older ones, with the ring tailed lemur being the only base game species. This is because, IMHO, Frontier has significantly improved their workflow, resulting in animals that are far better in most regards. I think the best showcase of this is to compare the Nile lechwe to the other antelope in the game, especially the ones lower on the list, or the water buffalo to the African buffalo
Great, minor tweaks: These are animals that are still great but with a few flaws that keep them from working their way into the premier echelon. For example, the red crowned crane is gorgeous but has some pretty awkward clipping when resting, a likely leftover from it being based on the flamingo. Even the Southern white rhino has somewhat stumpy legs (tho I think that depends on what specimens Frontier was using for reference) and the babies are small for the model (toddler model the size of a newborn). However, not bad overall.
They're ok, still improvable: These ones aren't TERRIBLE, but they could really, really, REALLY use some QoL updates, with the most common issue being very low quality textures when compared to modern cohorts. For example, compare the African savanna elephant and Indian rhinoceros to the later Southern white rhinoceros. The difference in texture quality is night and day. You also have issues of size (the hippo is FAR too big), texture (the great apes especially) and the rigs (The elephant rig has knees too low and the orangutan is far too similar to the gorilla). You also have a lot of cases where Frontier has made a very similar animal but just 10x better such as the water buffalo excelling over the African buffalo
Outright bad for various reasons: These animals have significant flaws that decrease their appeal. Examples include weird quirks with the rig (Formosan Black Bear never shutting its mouth and being overall quite glitchy), poor model quality (Plains zebra and the hyena), poor texture quality (the two birds), etc.
Sin: These are the worst of the worst. A combination of poor models, textures, and especially rigs that make these animals unusable without remaster mods. A lot of these are pretty obvious. The lion is universally considered far too cartoony for the slightly enhanced realistic style Frontier is going for, the snow leopard has the same issues, and the fact that the Malayan tapir hasn't received some form of QoL update is a real kick in the dishpan (Hoo hoo hoo).
If you want me to explain what I think of certain animals, let me know with a reply.