As for me, mine are:

Sandshrew line, Lapras, and Cubone line (Kanto)

Cyndaquil line, Mareep line, and Wooper line (Johto)

Mudkip line, Metagross line, Aggron line, and Flygon line (Hoenn)

Turtwig line (best starter!), Piplup line, and the Gastrodon line (Sinnoh)

Oshawott line, Roggenrola line, Scolipede line, Reuniclus line, Litwick line, and the Golurk line (Unova)

Espurr line, Flabebe + Floette (not Florges), and the Chespin line (Kalos)

Rowlet line, Lurantis line, Marshadow, Poipole line, and the Alolan forms of the Sandshrew line (ice steel is such a cool typing!) and Marowak (fire stick!) (Alola)

The Meltan line is also very cute, Gen 7 but technically not Alola

Falinks, Corviknight line, Snom, and Copperajah line (Galar)

Best legendary is definitely Kyogre, because whales are cool. Marshadow is second though. Volcarona isn’t legendary but would be the top pick if it was. Best starter is Turtwig, followed by Mudkip and Rowlet.