Legends and Gods
Core Gods
"The ones you can use as swears." The core gods rarely interact with the mortal realm, choosing to remain distant and focus on their aspects of life and the universe. Most of them are known the whole world over thanks to their influence and power, even though they are the hardest legends to interact with. They are capable of manipulating their elements and are not forces to mess with.
Arceus - The creator of all
Azelf - Guardian of Life Forces, Master of Determination and Willpower
Dialga - Time Incarnate
Giratina - Presides over Life and Death, Reincarnation, Souls, and the Distortion Realm
Mesprit - Guardian of the Flow, Master of Emotions
Palkia - Space Incarnate
Uxie - Chronicler of the World, Master of Knowledge
Secondary Gods
These gods might be worshiped or feared depending on their circumstances. They are gods in their own rights, and are located on the physical planes some of the time. Because of this, they can be very dangerous, especially the ones tied into the land, sky, and sea.
Celebi - Messenger of Time, Patron of Healing and Forests
Cresselia - Queen of Dreams, Spirit of the Moon
Darkrai - King of Nightmares, Bringer of Darkness
Deoxys - Messenger of Space, Monitor of the Space Continuum
Groudon - Titan of the Land
Kyogre - Titan of the Sea
Rayquaza - Titan of the Sky
Victini - Runner of the End Game, Judge of Souls
Held in High Regard
Legends who get actively involved in the lives of mortals. They aren't quite considered gods, but they are legends in their own rights, and their power and abilities are respected and acknowledged as such. They are sometimes seen as forces of nature, and are not always viewed in positive lights. Some of them rule cities, tend to forests, or look after sacred areas.
Articuno - Assistant to Lugia, Bringer of Winter
Diancie - Queen of the Crystal Kingdom, Co-Creator of Mega Evolution
Ho-oh - Bringer of Fortune, Chronicler of Tales
Kyurem - Judge of Rhyme and Reason. The Shell
Lugia - Guardian of the West Seas, Chronicler of Tales
Lunala - Creator of Planets
Manaphy - Assistant of Kyogre, Heart of the Sea
Meloetta - The Muse
Mew - Gene Bank, King of the Crystal Kingdom
Moltres - Assistant to Lugia, Bringer of Spring
Regigigas - Mover of Land, Patron of Innovation
Reshiram - Mother of Truth, Caretaker of Dragons
Sky Shaymin - Guardian of the Tree of Life
Solgaleo - Creator of Stars
Suicune - Assistant to Ho-oh, Purifier of water, the North Wind
Xerneas - Creature of Life, Holder of Immortality
Yveltal - Creature of Death, Reaper of Souls, the Corpse Swallower
Zekrom - Father of Ideals and Technology
Well Regarded
Not as well known as the higher up group, but still very powerful and important. Some are acknowledged as benevolent forces, others are folk heroes, and a few are the subjects of folk tales parents tell to their children to get them to behave.
Cobalion+Terrakion+Virizion+Keldeo- Regional Guardians of Pokemon, Heroes of the War of Life and Death
Entei - Assistant to Ho-oh, Story Collector, Storyteller
Heatran - Assistant of Groudon
Jirachi - Wish Granter, Miracle Worker, Star Child
Latias + Latios - Assistants to Rayquaza, Guardians of the Sky
Mewtwos - Keepers of Mega Evolution, Big Babies
Raikou - Assistant to Ho-oh, Storm Moderator, Story Collector
Regirock + Registeel + Regice - Defenders of the Tree, Fallen Guardians
Shaymin - Bringers of Flora
Thundurus + Tornadus + Landorus - Storm Makers, Wish Granters, Genies
Zapdos - Assistant to Lugia, Bringer of Storms
Zygarde - Maintainer of Balance, Fearsome Beast
Unknown
They're legends, but nobody's really heard of them.
Genesect - Created by Paragon. A father, husband, and brother.
Volcanion - The heatran claims to have found and hatched it.
Hoopa - What is this troublemaker?