I am kinda late now, but i will give my opinion on the starters.
Gen 1: The Bulbasaur line is my favorite line out of the three, this might be due to i picking him in FR, and i remember having so much fun with him, their design are so good, the Dinosaur feeling strikes me when i look into them, and i really like the flower on his back growing as it evolves, Red Saur can be a reason to why i like he so much to. I don't really like Charmander's line, ironiccally, because of the anime. We just see his Charmander going from a nice guy to a brat that didn't obeyed Ash, and that pissed me off at the time, since Ash and his friends saved Charmander, and he also maked Ash loses his first League, wich also pissed me off back in the day, while, yeah he get better over time, the damage was already done for me. Squirtle is alright, i've never have grown to love him, but i didn't hate it, i liked Wartortle more out of the three stages, and i kinda see some fun with him in FR due to not needing to catch a water pokémon with a rod to use Surf, though i always prefered Bulbasaur.
Gen 2: Problaby my least favorite out of all of them. While the Cyndaquill line have some nice desing choices, his desing was just to boring to me, though i loved Ash's Cyndaquill in the anime, i didn't really like him in the games, though he is my favorite out of the three. I just hate Meganium, her desing is even more bland, with only a Flower and an all Green body, and for me, a huge stap down from Bayleef's desing, and she is also really bad in general, in competitive and the games. I considered she the Hard mode, due to having so much trouble in the first Gyms due to the typing, wich maked me hate it even more. Totodile is alright, the desings really grown on me, problaby just because he is an Alligator, but he is, for me, the best one on this gen just because of the desing.
Gen 3: I really love this Gen, with Ruby being my first entry on the series of the games. Treecko's line is so good in desing for me, and the anime really maked Sceptile grown on me, and overall, i don't dislike nothing on their desing, he is just so cool for me. Blasiken is alright for me, but a good alright, i don't really like Torchic's desing but Combusken maked better for me, though after seeing with more open eyes, i don't know if i can see it the way i see it before, Blaziken is also cool for me, a really strong desing, his signature move and his fighting style that i imagined back in the day maked me remember of Sanji, so that is a plus. However, nobody can beat Swampert, he is my favorite starter so far, Mudkip is so cute and adorable for me, i also really like Marshtomp, though people say he is bland or derpy, and i can see that, and he being my least favorite Second-Stage of the three, i don't find it awful, however Swampert is different, even when i was little, i finded he so cool, and the typing and usage in Ruby really leaved a good mark on me, i am problaby being biased on him, but i don't care.
Gen 4: I liked to. Turtwig's line, while kinda bland on the beggining, is complemented by Torterra, my favorite Final Stage on this gen, i really love him and his desing, also, Paul's Torterra was also one of the reasons that i liked him, that mon was just so powerfull that bugged my mind that he didn't use against Ash in the Sinnoh League. Piplup is alright, though i don't like his first two stages, Empoleon is a great mon overall, with a good desing that just screams Royalty for me. Infernape is really good on all of his stages, and the anime also was one of the reasons that i liked he so much, his battle against Paul's Electivire was insane at the time for me, and he getting the win against him was so good to watch for me.
Gen 5: Kinda meh for me. Oshawott and Dewott have really good desings and cool concepts, then there is Samurott that it is just disappointing for me, i just seed so much potential for a samurai-like or just a cool Pokémon with a sword, but nope, he needed that break all of my expectations. Tepig is alright, he is cute as hell, but Pignite is... strange, i don't dislike him, but there is nothing to say that i liked him, however, Emboar is cool for me, and look at his shiny, it is so majestic. Serperior is a solid line, good on all three, but nothing that amazes me.
Gen 6: All the First stages are cool, nothing to complain there, the second stages are good, except for Quilladin, he goes from a nice Chespin to a fat one, Braixen is my favorite Second Stage here, she is just so cute plus, a good waifu overall, however, the Final Stages kinda sucked, except for Greninja, Delphox never grewn on me due to be such a stepdown for an amazing mon, Chesnaught is better than Quilladin, but still, not good enough to reverse what Quilladin did.
Gen 7: Rowlet's line is cool, Rowlet is cute, Decidueye has an awesome desing and Dartrix is kinda there, it also never grewn on me. Litten and Torrarcat are the best First Stage and Second Stage respectively, Incineroar is alright, however, i don't like him all that much. Popplio is bland for me, butr Brionne deserves to be killed with fire, that thing is ugly as hell, the worst Second Stage mon so far, and it better stay this way, Primarina is nice though, i can see some beauty there, and she seems like a good mon to use overall