Personally, mine is joint first between Sandshrew (the cutest), Espurr (most relatable), and Gastrodon.
After those, in no particular order, I like Turtwig (best starter, fight me), the Roggenrola line (little rock guys), the Litwick line (candles and lamps with nefarious intentions), and Metagross (cool robot thing).
Kyogre is the best legendary in my opinion
From the first game boy games I rolled a lot with Charichard and Nidoking, then did not play untill like a few years back and ran into Grimmsnarl and that is my favourite of the new ones.