Best:
Rock:
3 I guess.
We have a vast variety like Aggron, Lunatone/Solrock, Armaldo, Cradily, Rwlicanth.
Water:
Also 3. Some nice combinations and heavy hitters like Swampert, Ludicolo, Milotic, Sharpedo, Wailord and much more.
Electric:
7 I think with nice combinations like A-Golem, A-Raichu, Togedomaru, Viakavolt, Tapu Koko, Zeraora
Grass:
Maybe 1. We have Grass/Poison classics like Venusaur, we have a strong Exeggutor.
Poison:
Also 1. We have the mentioned Venusaur but also Nidos, Venomoth, Gengar, Tentacruel, Golbat, Muk. There never were so many Poison types in one gen.
Psychic:
1 for the 3rd time.
Alakazam, Slowbro, Exeggutor, Mr. Mime, Jynx. Not to mention how OP the type was in the 1st gen
Fire:
6 but mostly due to Megas. From standard pokemon we have some good ones like Talonflame and Volcanion. And from Megas we have 2 M-Charizards, Mega Blaziken, Mega Houndoom, M-Camerupt.
Ground:
I think 4. We have Garchomp, Rhyperior, Gliscor, Hippowdon and Gastrodon.
Flying:
6. Talonflame, Hawlucha, Noivern and some solid Megas: Pidgeot, Pinsir, Aerodactyl, Salamance.
Bug:
5. Volcanrona, Scolipede, Crustle, Galvantula, Genesect and some more.
Normal:
I think 1 Snorlax, Tauros, Kangaskhan, Chansey, Clefable.
Ghost:
7.D Mimikyu, A-Marowak, Pallosand, Marshadow.
Fighting:
6 with Hawlucha, Pangoro and Megas: Lucario, Blaziken, Gallade, Heracross, Luponny.
Steel:
Once again 6: Aegislash, Klefki and some Megas: Lucario, Mawile, Aggron, Metagross, Scizor, Steelix
Ice:
4 with some nice type combinations: Mamoswine, Weavile, Abomasnow, Frosslass, Frost Rotom.
Dragon:
6. Goodra, Tyrantrum, Noivern, Dragalga are all solid. Add Mega Altaria, Salamance, Lati@s and top with Rayquaza.
Dark:
I believe that 5. Hydreigon, Zoroark, Bisharp, Scrafty, Mandibuzz and Krookodile.
Fairy:
6. Not counting re-types we still have some solid Players like Florges, Sylveon, Klefki,Xerneas, Diance. And some good Mega: Garderovoir, Altaria, Mawile and Diance once again.
