Finally! You're here, Mt. Silver. Now, I came here around 20-30 levels under the the "norm", as it adds to the challenge.
Venasaur - 2 Flamethrowers from Houndoom.
Blastoise - Spam Thunderpunches from any electric.
Charizard - Use Surf, or Hydro Pumo if you have it.
Pikachu - One Hit KO from an Earthquake.
Espeon - Spam Crunch.
Snorlax - No definitive strategy. I was lucky Rest wasn't used. Just use your most powerful attacks, or go in with a Rock Type to balance it out.
Then you win. And my Pokemon Gold & Silver Boss Guide comes to an end. Goodbye!