I'm not going for just the first stage, but for all members in each evolutionary line.
19. Chikorita, Bayleef, and Meganium
Not that I hate them; it's just that I don't really find them interesting in many ways. It's just bland and deserves a mega.
18. Chimchar, Monferno, and Infernape
I just don't like how they imitated the Torchic line. They don't even have an ability as great as them.
17. Tepig, Pignite, and Emboar
I just find their designs a little too...out. Also I'm kinda sick of the Fire/Fighting trend.
16. Cyndaquil, Quilava, and Typhlosion
I just can't seem to like these starters as much as I love others. Must be their competitivity.
15. Totodile, Croconaw, and Feraligatr
They gave these kickass-looking things the same treatment to be given to all starters, and I find them a little boring.
14. Treecko, Grovyle, and Sceptile
Though Mega Sceptile had a cool typing and Grovyle had a huge role in PMD, I didn't find them so great.
13. Fennekin, Braixen, and Delphox
Somehow disappointing starters. While the Fire/Fighting trend ended here, they're just not as usable as the other two members of the group. Must be because of Magician.
12. Charmander, Charmeleon, and Charizard
I don't like how popular this line is. I like how usable Charizard is, but mostly the only thing I love about the line is Charmeleon.
11. Squirtle, Wartortle, and Blastoise
Same as above, though not as popular.
10. Oshawott, Dewott, and Samurott
They're meh. Cute but not usable.
9. Turtwig, Grotle, and Torterra
Grotle and Torterra's designs kick ass. Also I like the signature typing.
8. Piplup, Prinplup, Empoleon
Prinplup is probably the best part in the line. I like Empoleon almost as much as Prinplup, and it's like Torterra, only there's a historical reference. Also Piplup is cute.
7. Mudkip, Marshtomp, and Swampert
Mostly I like the line because of the Mudkip and Marshtomp memes.
6. Torchic, Combusken, and Blaziken
Great ability, great designs (except Combusken because it looks like...a weird bird), great everything. I mean good.
5. Pikachu (not Raichu or Pichu because they're not available in Yellow unless you trade and because it's a Gen II Pokémon, respectively)
I find it cute and cool.
4. Froakie, Frogadier, and Greninja
Protean FTW!
3. Bulbasaur, Ivysaur, and Venusaur
I mostly love Mega Venusaur. I also love the fact that Bulbasaur starts off dual-typed.
2 and 1. Chespin, Quilladin and Chesnaught AND Snivy, Servine, and Serperior
I LOVE using these starters.
The Chespin line is fun to use because of Bulletproof and Spiky Shield. I also like how Chesnaught looks...Mexican.
The Snivy line. Why? Contrary + Leaf Storm.