Each generation of starters has brought something new.
RBY- Bulbasaur, Charmander, Squirtle (Venusaur, Charizard, Blastoise) The first generation. These Pokemon were not great in the first generation, but improved in the later generations.
GSC- Chikorita, Cyndaquil, Totodile (Meganium, Typhlosion, Feraligatr) Weakest generation. None of these Pokemon have ever been above the BL tier, and probably never will be.
RSE- Treeko, Torchic, Mudkip (Sceptile, Blaziken, Swampert) The best generation. None of these has ever dipped below the BL tier, and Swampert has become a staple OU Pokemon.
DP- Turtwig, Chimchar, Piplup (Torterra, Infernape, Empoleon) The newest generation. This metagame brought some interesting changes, and these Pokemon show that.