If you don't want to trade either, I would say Typhlosion, Tyranitar, Ampharos, Dragonite, Poliwrath (Feraligatr if you want to trade) and Alakazam, but that's just my opinion.
Chat with our AI personalities
No, you cannot breed Legendaries with the exception of Manaphy.
Mt. Silver or the Pokemon league
Disregarding Legendaries, the most powerful Pokemon by stats is Slaking. Although Nature and IV's also have a lot to do with it. It all depends on the stats you like.
no legendary:gyarados legendary:lugia -megaman9999
sorry you have to trade it to Pokemon soul silver