I do agree, I mean I could be more creative than that. Seems like the first generation was focused with thier 3 Legendaries as bird (yea pointed out the obvious) But the had Similarities to Mythical creatures. Like the Pheonix, Fire Bird, etc. Then the Legendary "felines" whatever you want to call them. Entei looks lionish, Suicune, looks like a Panther a little, and Raikou looks like a Tiger, even has stripes like one.
Then the Regis came, all of them were based on Minerals. Ice, Steel, and Rock. These 3 Psychic Fairy, cat things. Are vastly different in some ways. Like Ive noticed in my game; the yellow one is more tankish, and can take hits really really well, be used as a good tormentor. Then the blue one seems to focus more on attacks than the yellow, with weakish defences. The Pink one I have not tracked down yet, since you can only find that one in the wild.
The point to what I am saying, they could have, since they already made elements and minerals, made something like spooky. Like a Ghost, Dark, Psychic set of 3. For the other ones, Diaruga, and Parukia. Darkrai, Sheimi etc. Seems alright. Cause they have to have something to base a newer movie on. Since theyve had a movie with most of the existing Legendaries in it, except Kyogre, and they only put Raikou in a special episode.