I've only played the original Pokémon Red from the original Game Boy, but from what I understand, the basics of gameplay have remained through the years, though the number of species has grown from 151 to over 700. Though "species" is a word I hesitate to use because of one of the series' most fundamental aspects, the poorly named "evolution."
(All images taken from Bulbagarden.)
What the series calls evolution would be better called metamorphosis, as a single creature changes its form dramatically over the course of its life cycle, like a caterpillar to a butterfly or a tadpole to a frog. For example, I like how the weak Magikarp, resembling a fish, transforms into Gyarados, a powerful creature resembling a Chinese dragon. There aren't many works of science fiction that come immediately to mind that use metamorphosis, and I think the basic concept is something with a lot of potential when creating a fictional world.
However, this means that Magikarp and Gyarados are the same species, just at different points in its life cycle. So the number of Pokémon species is likely a lot lower than the number of what people call "Pokémon."
Another aspect of the series that appeals to me is the creatures that are part animal and part plant. Most of these are "Leaf-type," such as the Venusaur family, or Oddish and its evolutions, which make me think of Pikmin (heeeey...)
I've always wondered what kind of conditions would give rise to motile plants. Even on Earth, in regions with wildly varying seasons, plants would rather stay put and go dormant than move. (Maybe that's for the best...)
Vulpix and Ninetales make me wonder why we never see animals on Earth with more than one tail.
Nidoking and Nidoqueen bring to mind the concept of sexual dimorphism, where the males and females of the same species look markedly different.
Metagross just looks cool; a giant quadruped crab.
Gigalith looks similar, with an exoskeleton that seems to serve as camouflage in a volcanic environment.
As does Scyther, with its exoskeleton and massive claws.
For some reason, though, my favorite Pokémon is Lapras.
It has no evolutions, it's just a plesiosaur with a turtle shell, that's capable of being domesticated and ridden across the ocean. The only way it could be better is if it could fly. A simple yet creative design with appeal to one's inner child, and in my opinion, a good example of what makes Pokémon so popular.
However, this means that Magikarp and Gyarados are the same species, just at different points in its life cycle. So the number of Pokémon species is likely a lot lower than the number of what people call "Pokémon."
Another aspect of the series that appeals to me is the creatures that are part animal and part plant. Most of these are "Leaf-type," such as the Venusaur family, or Oddish and its evolutions, which make me think of Pikmin (heeeey...)
I've always wondered what kind of conditions would give rise to motile plants. Even on Earth, in regions with wildly varying seasons, plants would rather stay put and go dormant than move. (Maybe that's for the best...)
Vulpix and Ninetales make me wonder why we never see animals on Earth with more than one tail.
Nidoking and Nidoqueen bring to mind the concept of sexual dimorphism, where the males and females of the same species look markedly different.
Metagross just looks cool; a giant quadruped crab.
Gigalith looks similar, with an exoskeleton that seems to serve as camouflage in a volcanic environment.
As does Scyther, with its exoskeleton and massive claws.
For some reason, though, my favorite Pokémon is Lapras.
It has no evolutions, it's just a plesiosaur with a turtle shell, that's capable of being domesticated and ridden across the ocean. The only way it could be better is if it could fly. A simple yet creative design with appeal to one's inner child, and in my opinion, a good example of what makes Pokémon so popular.