If you want a strong Grass Pokemon, around the second gym you'll get access to Petilil (limited movepool, but can status the enemy and stat up to murder everything) and Sewaddle (Bug/Grass, good Speed and Attack, reasonable movepool).
If you want a strong Fire Pokemon, after the third gym you'll get access to Darumaka, who is a bit of an iffy Pokemon until it evolves. After it evolves it will eat enemy Pokemon.
Water is harder to replace, but if you choose Snivy you can get a reasonably strong (albeit fragile) Panpour, and around the second gym you can get Tympole, who evolves into a nice and average Water/Ground.
"Murder of the living is tragic, but murder of the idea is unforgivable." - Janus, speaker of the synod
I don't get why Samurott gets so much hate for in-game. He has high special attack, is pretty bulky, and has okay speed. Maybe he's outclassed competitively, but as a starter, he does a good job. But if you don't like his design, well then there's nothing I can say there.