I would have written a critique for this if you asked for one!
It looks very nice. Well, it's from you so of course it looks nice. I like how you used different shades for the hair on the red dragon. And for the green dragon, I admire how you added the "bony" texture to the spikes and chest plates. It shows age, adulthood. And I like the sizing of the scales according to their placement on the dragon. The noses look nice too, the simple shape of them but still fits well.
The blue hair on the red dragon (bottom left of image) looks a little too simple, and the image could use a background even if it's a simple one.
How is it that everything looks better in couples Is it the fact they are close, the colors, the fact of what this image is meant to represent, No I think it is a combination of all three plus. In vision I like the style, as well to the form that the red one on the left looks Asian, and the green one one the right appears as western to me. Now the fact is this all could be just guesses as the red one is actually Asian am not for sure but still al the same, an excellent image.