Venusaur is the best of its gen
Meganium isn't bad despite being lower than Typhlosion and Feraligatr
Sceptile isn't bad, better than Swampert and not as cool as Blaziken, but all three are decent-to-middling
Torterra >>>>> Infernape, though he can't beat Empoleon in design, obviously
Serperior is undoubtedly the best in Unova, even if Samurott is also pretty cool
Chesnaught has a really solid design alongside the other two gen 6 starters
Decidueye is undoubtedly the best from Alola, even if Primarina is OK.
Grass is generally the best starter, so idk how you get the idea it's the worst.
for reference:
Venusaur > Blastoise > Charizard
Typhlosion > Feraligatr > Meganium
Blaziken > Sceptile > Swampert
Empoleon > Torterra > Infernape
Serperior > Samurott > Emboar
Greninja > Chesnaught > Delphox
Decidueye > Primarina > Incineroar
