What pokemon you would use for competitive battling? (Not including legendaries)

I played only first Pokemon game so I used Blastoise, Charizzard and Venosaur. Also Mewtwo and 2 legendary birds Zapdos and Articuno but you said no legendary creatures... So I would replace them with Scyther and probably some crazy psychic like Gengar or Alakazam. Adding Ditto could be good idea to copy his strongest. Or wait, wasn't Porygon the one that copied? lol I don't remember anymore...

to be honest, im not familiar with the new pokemons on Diamond and pearl and suggest to stick to old poke games.. Tyranitar Dragonite Venusaur Electabuzz Feraligatr Typhlosion

For competitive battling, my nephew would advise me to use Infernape (favorite), Empoleon, Torterra, Salamence, Magmortar and Electivire.