War of the Monsters is an amazing game for the Playstation 2. Imagine Street Fighter 2 mixed with Rampage, put it in 3d and give it a 50s creature feature theme, and you have WotM. The action is fast paced and easy to learn with many different monsters to choose from. You can also unlock new looks for each monster as well. The very cool cut scenes are done in the style of old movies. It my humble opinion, it is probably the best giant monster game to date.
The monsters are unique, yet still mirror famous monsters. There is a giant ape(with mecha version unlockable), a dragon, giant bugs, a japanese style robot, a rock monster, a godzilla-esc creature, a lava monster, and a Mars Attacks style alien.
Another unique feature to the game, unlike Rampage and other monster fighters, is that there are unique boss fights which require strategy, rather than just button mashing. One of which is a giant mutant venis flytrap that grows out of an nuclear meltdown. So this game has more to offer than your typical fighter.