What type of Pokemon do you need for soul silver?

Answer 1

You should have at least one water-type, one flying/dragon (to teach HM2 Fly), and Pokemon that can learn Strenght, Rockmash and other rock-type of HM's (like Rock- or Fighting-type).

I like to have one of each of these's types:

Grass (with HM1 Cut)

Fire

Flying (with Fly)

Water (with Surf)

Electric

Dragon/Normal/Legend (Like Suicune, Entei, Raikou/legendary birds)

But these all have simple weaknesses, like fire to water, grass to fire..

Best is to get some ghost, fighting, dragon and normal type of pokemons that doesn't have any simple weaknesses, for example any physical attacks (like Tackle or Quick Attack) won't do to ghost-type, only Special Attacks (like Flamethrower, Ember, ThunderShock, RazorLeaf..) but you should really remember that more far the game goes, more special attacks will be used, especially with Elite 4.