R8 my taste /v/:
>Weather Trio > Creation Trio+ Arceus > Sky/Ocean Duo = XYZ Trio > Stellar Trio > Tao Trio
Weather trio has a nice balance of pleasing designs that make them feel ancient and primal, neat, if basic concepts, and decent lore. Creation trio has the best lore by a giant mile with a ton of stuff to it, and Giratina is the most well executed legendary in the series, and Arcesus's design does a good job of actually feeling celestial and holy without just being angellic and still feels alien, but Dialga and Palkia are a bit of a mess.
Ho-Oh and Lugia, like the weather trio, have a nice balance of good designs, decent lore, and neat concepts, but Lugia has no lore, only ho-oh does, and there's not as much meat to them in terms of concept. The XYZ trio has problably the second most thought out lore behind the creation trio and good designs, but they lack the same presence a lot of the other trios have and Zygarde feels too much like an odd one out.
We don't really know enough about the Stellar trio to comment yet, and the Tao trio is visually a mess, with not that much lore and questionable concepts.
Also, bonus rankings:
>Legendary Beasts > Legendary Birds = Legendary Golems > Swords of Justice > Lake Spirits > Tapus > Legendary genies
>Mewtwo > Arceus > Deoxys > Gensect > Hoopa
>Jirachi > Mew > Celebi > Marshadow = Manaphy > Shaymin > Vincti > Diancie > Kieldo
>Moon Duo > Eon Duo
