I'd be pretty happy with a pack each for New and Old world monkeys.
For the New World Monkey Pack:
- Golden Lion Tamarin: Famous and beautiful conservation species that brings a mini-monkey rig
- Geoffroy's Spider Monkey: These would be so cool if possible
- Cotton Top Tamarin: Tamarins are so common that at least a second species could be justified. This one isn't as popular or famous, but it is very common in zoos.
- Black Howler Monkey: The most popular South American monkey would add to the soundscape.
- Common Squirrel Monkey: These are adorable and pretty basic.
- Emperor Tamarin: Another good tamarin that actually lives in the Amazon.
- Red Uakari: It would add a very odd oddball.
- Honorable mentions white-faced saki, tufted capuchin, night monkey, titi: The first two are zoo staples and great choices to include in a primate lineup. The other two are cool.
For the Old World Monkey Pack:
- Mantled Guereza: This is the most popular of the zoo classic African monkeys, another unaddressed niche.
- De Brazza's Guenon: A second African monkey would be great for variety and bigger zoo sections.
- Barbary Macaque: Europe's monkey
- Grey Langur: Famous Indian monkey that adds a classic langur
- Golden Snub-Nosed Monkey: China's monkey
- Red Shanked Douc: My favorite old-world monkey
- Lion-Tailed Macaque: Another iconic one for India and adds a tropical macaque
- Honorable Mentions: Patas Monkey, Grivet Monkey, Wolf's Guenon, Aye-Aye, Gelada: More African monkeys would be good, I like the idea of a nocturnal primate, and the gelada is popular.
If I could only get one, I'd try to cover the zoo classics and regional picks.
- Mantled Guereza: I need at least one 'classic' African monkey. It's a pretty basic zoo niche. I might personally trade one of the next 3 for a similar De Brazza's guenon, but I want everyone or at least as many as possible to be happy.
- Golden Snub-Nosed Monkey: This seems to be the animal, not just monkey, that Chinese players want most.
- Barbary Macaque: If everybody else is getting monkeys, Europe should get its monkey, too. The Iberian Peninsula could use a thing.
- Grey Langur: India needs one
- Black Howler Monkey: Popular South American Monkey
- Geoffroy's Spider Monkey: Cool South American Monkey
- Common Squirrel Monkey: I want tamarins more if I have to choose, but this one's also cute and basic
- Tamarins, including the Golden Lion and Cotton Top, in lieu of exhibit animals or scenery: Tamarins are very common in zoos, and I miss them almost every time I play.