There are no real front-runners on my list, so even the lowest-ranked pack isn't that much worse than, say, #5 on my list. #1 to #3 are pretty much interchangeable. But here we go:
8. Arctic Pack – I want to jump at this pack's defense whenever I see people outright trashing it, but then I remember that I really don't use three quarters of this pack at all. The dall sheep is my favorite by a wide margin, and I use it in almost all of my zoos. The reindeer isn't too appealing to me, the polar bear is a great animal that I don't really care about too much and have not put into any of my zoos so far, and the arctic wolf is an animal that I have somewhat warmed up to, but still never used regardless. The building pieces are very useful to avoid climbing animals escaping their habitats, but other than that, the pieces are not really my go-to building items. So, last place it is for this pack, even though it still has quite a bit going for it.
7. Africa Pack – this was a tough choice for me to make, but ultimately I came to the conclusion that I liked the other packs more than this one. The building items are all beautiful, but I rarely use them, and while all the animals are utterly fantastic and perfect representations for the African continent, I still felt a little underwhelmed considering that there would be so many more African species to choose from (I'm still sad at the possibility that we might never get secretary birds or servals in the game). The four animals are all some of my favorites, but the building items themselves did not convince me as much as in other scenery packs, even though I can remember a lot of praise for its versatility when it came out.
6. South America Pack – what is in here is great. I love all the animals (even the llama, even though I would have loved to get a guanaco instead), but what's missing is key here. The severe lack of South American fauna in the base game was not really compensated by this pack, and although the Aquatic Pack made up for that to some extent, there are still some iconic species missing. If we had gotten three more species in the base game, such as one more new world primate and something like the spectacled bear, patagonian mara or greater rhea, that might have made me less grumpy at the SA pack for being so slight in terms of much-needed SA representation. Still, the downside of this pack is what's missing, and not what's there, because I really like the building items and frequently use all the animals in here.
5. Aquatic Pack – it's probably unfair to not rank this in the Top Three, but my main complaint about this one retrospectively is that all the animals in here except for the otter have more interesting alternatives by now, and if the Asian Small-Clawed Otter made it to the game, that would make it four. Don't get me wrong, I like all the animals in this pack, but sea lions, african penguins and alligators seem more serviceable to me than seals, king penguins and caimans. That said, I still dislike that we got the grey seal over the harbor seal, and would have loved another Antarctica penguin species (gentoo or southern rockhopper) to put into mixed habitats along with the king penguin. But I guess we'll have to rely on mods for that. Still: the building items are incredible, and I loved the pack when it came out, so the negatives are only mentioned because I needed to somehow explain not putting this on the top of this list.
4. South East Asia Animal Pack – most people rank this lowest, as far as I can tell, but I love almost all the animals in here. The sun bear, binturong, dhole and babirusa are all animals that I couldn't imagine my zoos without anymore (with babirusa & sun bear turning into some of my all-time favorites in the game, and the dhole a rather surprising inclusion that I warmed up to quickly, and now consider my favorite canine in the game second only to the arctic fox). The clouded leopard would join those afore-mentioned species if it wasn't so bugged, and the malayan tapir if it was a better model. The proboscis monkey is a great inclusion, but I have to agree that it's not very useful for making general zoos, and a more generic primate species might have gone a long way to make this more utilizable. Having the komodo dragon in here and one of the other animals (e.g. the tapir) in the deluxe edition instead might have made it more appealing to people as well.
3. Australia Pack – second best scenery pack, in my opinion. The building items are fantastic and very useful for themed areas, and the animals are great all around. Even though more animals from Oceania are still missing and the dingo was an annoyance for many, I can't find myself disliking any of the additions in here, and the kangaroo is still one of my favorites. Would have loved a wallaby as well, but understand why it wasn't included.
2. North America Animal Pack – all-around amazing animal choices. Some people criticize the inclusion of the arctic fox, but I'm so thankful we finally got it, and I love all the other animals from this pack as well. In retrospect, even though I was against it at the time, I think I would have appreciated an American Black Bear as a "clone animal" as well to get more versatility for NA sections, but I wouldn't really know what to replace in this pack.
1. Europe Pack – might be recency bias, but this was the perfect pack for me. The building items and scenery pieces are so useful and interesting, but it's the animal line-up that makes this so great for me. All four of these animals, the ibex, the lynx, the beautiful fallow deer and the badger are now integral staple animals for my zoos. There is not a single thing I would change about it, and I was over-the-moon excited when it came out.
Time to update this ranking! What a long way we've come since my last ranking.
20. Barnyard Animal Pack
A fine pack that I've never used so far, so my opinion might still change once I do. Domestics were never high on my wishlist and the species choices felt particularly weird to me. But there are some nice and useful scenery pieces.
19. Arctic Pack
Still on the lower end of packs for me. I still don't like the Arctic Wolf, mainly because the base game wolf looks so bad and downright forces me to use the Arctic Wolf instead. I like the dall sheep, but now that we have received better caprine alternatives, the lack of Musk Ox is very noticeable.
18. Zookeeper's Animal Pack
All seven animals are great choices, but they don't work very well together. They were obviously developing a Highlands Pack at one point - just go for it rather than shying away halfway through.
17. Americas Animal Pack
Some very useful additions along with some less useful ones, with the much-discussed lack of a coati as its most glaring shortcoming.
16. Tropical Pack
I like the individual parts of this pack. All five animals are great choices (I even warmed up to the monitor), and the scenery is good-looking. But I don't think the individual elements come together well into a cohesive whole. The entire pack feels all-over-the-place, and considering how many tropical animals were needed at the time (and still are), this arguably should have been an animal pack.
15. South America Pack
This has aged rather badly for me. I don't use the scenery pieces whatsoever and dislike their textures, for some reason. The animals are all good and necessary, but they should all have been in the base game to give us a head start on SA animals and allow us to get more SA representation through this pack. My suggestion: keep the Jaguar as headliner, move Llama and Capuchin into the base game, and then have a pack with Jaguar, Anteater, Squirrel Monkey and a Caiman species. That scenario would have been super-useful at the time.
14. Asia Animal Pack
Six undeniably great animal choices, but the pack as a whole is held back by the elephant as a truly baffling choice. Can't comment on the scenery yet.
13. Aquatic Pack
My issues persist: the Seal and Caiman have gotten better alternatives since, and I still think the Grey Seal should have been the Harbor Seal. I love the scenery, though. Move the Caiman into the SA pack, replace the seal species and add a bird (either a duck, swan or even a pelican) and this would have been an undeniable banger for me.
12. Southeast Asia Animal Pack
I understand the general sentiment towards this pack, but I continue to have a soft spot for it. All the animals are extremely useful to me.
11. Australia Pack
Fantastic scenery and animals. I loved the addition of the Cassowary at the time, still do. Further Australian additions have only made this pack more useful over time.
10. Africa Pack
I'm ranking it a bit higher this time around because the selected animals are great choices and the scenery is so useful. In retrospect, maybe the Fennec Fox fits better into the Arid pack, opening up a spot here for another animal, but I loved its inclusion at the time.
9. Arid Animal Pack
Another pack that grew on me a lot. The Somali Wild is one of my Top Three favorites in the game, and all the other animal choices are equally useful to me. I just felt (still do) that this pack could have been better by going for a more global roster.
8. Oceania Pack
Love the scenery, love the summer vibe, all the animals. A really good pack all-around.
7. Eurasia Animal Pack
A great pack that feels upstaged by the weird inclusion of the Sloth Bear. But I love all the other choices (even the saiga).
6. Twilight Pack
A pack that is only getting stronger over time. I felt like the animal roster should have been more global (the lack of Fossa was my main regret of the time), but all the animals are frequent go-tos in my builds, and the scenery is so useful.
5. North America Animal Pack
In short: a wonderful roster. Great pack.
4. Wetlands Animal Pack
I was a bit skeptical of the animal choices when it came out, but it holds up with a truly wonderful roster that actually feels diverse and global. At the time I was mostly mad to get another caiman, but it's now my favorite reptile in the game.
3. Conservation Pack
Second-best scenery of the game. Plus, there are no complaints with this insanely strong animal roster. The siamang has gotten a stronger alternative since, but remains nice to have. I also love the Oryx, Przewalski's Horse and think the Amur Leopard is one of my three favorite cats in the game.
2. Grasslands Animal Pack
No complaints. This is the best animal pack, without a doubt. Every choice a heavy-hitter. I loved this pack a lot when it was released, still do.
1. Europe Pack
It remains my favorite of the original continent-based packs. The best roster, and the scenery is outstanding. The European Marquee Beam has to be my most-used piece. Probably my most used DLC overall up until now.