Oh No! There goes Tokyo!
I feel that no game has gotten it right in regards to what it would be like to control Godzilla and his kaiju cohorts, but Pipeworks' titles come close. Unleashed is the culmination of the best of these titles.
The Wii version only uses motion controls, so it's quite troubling to get used to movement and attacking. Once you get the hang of it though, it becomes second nature.
Besides the control issue, the Wii version definitely comes out on top. The graphics are slightly better, and it has more (and cooler, in my book) exclusive characters than the PS2 incarnation. If you're a huge Godzilla fan, you'll definitely want to pick up both if you can, to experience the different characters, but if you have a choice, go for the Wii. If you have the patience to learn a slightly obscure control system, it is very much worth the effort to lay your foes out with King Caesar or the original Godzilla.