I am only a fan of Articuno as far as the birds go. It is beautiful and elegant and expresses ice in a more nuanced fashion. Also, just look at all of their tails, Articuno's is gorgeous, the others are just...there. Moltres, is just blah to me. It's just so literal, I am a fire-bird. Zapdos, I just feel ambivalent about it. It's just a bunch of generic lightening zigzags that form a bird. Though I prefer the beast, I did enjoy the Pokemon: 2000 better! But I would only attribute that enjoyment to Articuno and Lugia.
Suicune is just beautiful. Arguably one of my favorite Legendary's along with Cresselia, Mew, Reshiram, and Virizion. With flowing wisps, diamond accents, purple head piece and cape, it should equal a messy disaster, but Suicune looks flawless and tranquil. Entei is also a great pokemon, but he's not as perfected like Suicune, though I still love the handle-bar mustache, yellow crown, and red facial features against his brown coat. I am not terribly fond of Raikou, nor am I totally off put by it. The purple cape, blue tail, and grey face fur clash with the beautiful stripes, blue whiskers/gray headplate, and fangs. It doesn't feel cohesive. As a trio, the beasts seem better designed.