All fail.
Grass is the best starter pokémon in Red/Blue for 1 reason only.
It will literally rock ''Brock'' and ''Misty's'' socks.
And Lt with lighting isn't that hard with it either.
And in the end you only need your Venusar and Gyarados which will rape em all because of it's possibilities.
The Gyarados can use moves such as Fire Blast (Fire), Hyper Beam (Normal Critical Move), Ice Beam (ice, also perfect versus Lance dragons), Thunder (Lightning), Hydro Pump (Water), and many many more moves including powerful dragon moves..
Now add the fact that you will spam buff Gyarados with HP Up, Protein, Iron etc etc... It will became a incredibly powerful pokémon which will handle all possible situations.
And then as your 3rd pokemon and last one you might consider a Moltres or something just as a backup pokemon to revive the other pokemons.
So Venusaur, Gyarados and any other pokemon will rape Elite Four and all and everything.
End of story. Gyarados is imba and will rape your parents while you cry for pikachu to help.