My opinion is pretty botched by the fact that I will only like a starter set if I like the designs of all three Pokemon. If we're talking raw battle ability, one can't deny that Gen 3 made some very powerful starters. But the last generation that I definitively liked the designs of all the Pokemon was Gen 2. The only reason why I don't add Gen 3 is because Blaziken was the first big change in fire starter designs that I didn't really care for, which is a shame because Swampert and Sceptile look great. The Gen that came closest to me liking all the starters again was Gen 6.
Then Gen 7 was a huge letdown for me purely due to Incineroar. I know you like this one OP, but hear me out. I was hype for a lion/cat based fire starter for years, and when it finally happens, the legitimate fire lion is a low-tier Pokemon, and Incineroar blue balls me by suddenly standing upright.
I attached a picture to merely point out what could've been for poor Incineroar, at least it's what I prefer.