Entei and Raikou are cat-like but Suicune is based on something more supernatural. Meaning there is no "overall theme" to them, like the Legendary Birds in the previous Gen.
And then there's this...
"Entei (Japanese: エンテイ Entei) is a Fire-type legendary Pokémon.
It is not known to evolve into or from any other Pokémon.
Along with Raikou and Suicune, it is one of the legendary beasts created by Ho-Oh after the burning of the Brass Tower. Out of the three beasts, Entei is said to represent the flames that burned the Brass Tower. "
This is on all three of their pages, just personalized for each one.
Can we STOP this "debate" now? They're neither all cats or all dogs or all anything else.
Yes, consider this debate over. Thank you for all this information.
Entei is based on the Shiisa which are half dog, half lion Raikou is based on the Raijuu and Suicune is based off the...Kirin...Qirin...Killin...there's a lot of spellings, I forget which is accurate.
So yeah, legendary beasts really is the most accurate, as Entei is the only one directly based on something that is even part dog (though Raijuu are said to take forms of many different animals, including dogs and canines)
Don't forget to check out my MegaTen themed webcomics at http://www.drunkduck.com/user/Strain42/ (Currently Updating: Persona 4TW Add-On M-F)