I’m not a huge Pokémon fan but I did recognize quite a few Pokémon in the movie Pokémon: Detective Pikachu like Bulbasaur, Charizard, Snorlax, Pikachu (of course) and a few others as well.
But were there any new Pokémon that were created just for the the movie?
No, every Pokémon that appeared in the movie is one of the 809 that have appeared in canon thus far1.
Detective Pikachu includes Pokemon from every generation of Pokemon games to date aside from the unreleased Pokemon Sword and Shield. Many of these Pokemon appear throughout Ryme City, walking or flying among humans and other Pokemon. Others appear in posters and signs or are otherwise mentioned in the movie, which means they exist in the world somewhere. This feature includes every single Pokemon or Pokemon mention we found in Detective Pikachu.
From the article, there are 56 different actual Pokémon shown in the movie. (The remanining 41 are depicted in signs, balloons, T-Shirts, posters, etc.)
And coming from one who has watched the movie as well, I can confirm that there are no new Pokémon that appeared exclusively in Pokémon: Detective Pikachu.
Notes
1 The 809 total includes Meltan and Melmetal which are first introduced in Pokémon Go.
