What if its meant to be both? A really good way to look at this would be to find a picture of the ruin and then see if there is one in the middle (hints at Arceus and Cynthia's solution) or two (which proves Cyrus right). It could be like the Stone Table in Narnia that has the two meanings upon it.
BRING BACK DEXTER!!!!
Well, in the game graphics we never see it clearly. In DPA it's very VERY clearly the fairies but they're around a symbol. Cynthia's grandmother says that those three are the key to controlling Dialga. But this is volume two, and Platinum hadn't come out yet.
Not to mention that in the anime, that same mural in the Celestic Town ruins shows the 3 Pixies on the outside of the triangle, and a shiny orb thing in the middle too. I can't even remember if they discussed what that orb in the middle is supposed to represent in the anime either. If they did, I completely missed it...
"He just put on 300,000 pounds....I'm SO jealous." Raven, Teen Titans
Have you heard of the saying "opening a can of whoop-ass"? I did that once in a dream.... I opened an aluminum can labled "whoop-ass" on somebody, and they disintegrated.
My favorite Bulbagarden smiley: