I have bias towards water starters, these are my choices for each gens and regions:
Kanto - Squirtle, a literal tank, with decent attacks stats to back up, and it has less weaknesses than the other two as pure water type
Johto - Totodile, for me it is cutest of all three, and relatively versatile learnsets for three pure type starters
Hoenn - I had used three of them in different playthroughs of Emerald, and i honestly would settle for any of them
Sinnoh - This trio is by far my favourite starters as a whole, but if i have to go with the most favourite, i would say Piplup, i had been holding out for penguinn based mon after Delibird before gen 4 came out, and Piplup just did it , i like Empoleon's design, and it is functional as special defense wall while boasting a good special attack
Unova - Oshawott, water type starter bias and all round mixed attacker, with decent bulk, Samurott has a cool design
Kalos - Fennekin, as an exception to my water starter bias, since psychic type comes before water type, and Fennekin entire evolutionary line is great as a whole, i dont hate Delphox design per se though it could have some space for improvement