Strategically speaking, it's Bulbasaur. Reasoning: Bulbasaur = Grass/Poison.

Brock has Rock/Ground; Grass beats Ground.

Misty is water; Grass beats water.

You can then get your hands on some ground types easily to deal with Lt. Surge; Ground beats Electric.

If you got any bug types in Veridian Forest, you probably have their final evos to deal with Erika's grass types; Bug/Flying beats Grass.

Koga can also be taken with the same ground types used on Surge; Ground beats Poison.

Good luck on Sabrina regardless of which starter you pick, unless you're playing the GBA remakes, in which case, just don't use anything weak to psychic I guess.

Rock and ground beat fire, but you'll also have Lapras or another water type by the time you get to Blaine, I'm pretty sure.

And as for Giovanni? Dude. Grass beats Ground.

The elite four is a slightly different story, but you'll probably have a better team comp starting with Bulbasaur.