The joys of Pokemon can be a difficult thing to explain to those who haven't been hooked. From a distance, the core Pokemon games look like standard-abiding Japanese role-playing games, and the changes that the series has undergone over the years have usually been subtle. The pieces might not be revolutionary, but they fit together with a precision that makes for an RPG experience that's accessible, highly engaging, and lasts a long time.
Pokemon Battle Revolution is the latest in a series that started with Pokemon Stadium on the Nintendo 64. Essentially, it is a single piece of the Pokemon experience--the actual Pokemon fights--that has been brought to the Wii and polished up to a high shine. The thing about Pokemon Battle Revolution is that, without any greater context of a grand adventure, Pokemon fights are kind of boring. Furthermore, the game's connectivity with Pokemon Diamond and Pearl for the DS ends up being a crutch. If you haven't already made the investment of time and money into one of those games, there's not much to get out of Pokemon Battle Revolution.
You won't get the most out of Pokemon Battle Revolution without a DS and a copy of Pokemon Diamond or Pearl.
Pokemon Battle Revolution takes place on the island of Poketopia, a place where Pokemon trainers can go to battle other like-minded Pokemon trainers to their hearts' content. There are a few ways you can go about this, though the best of them involve interaction with Pokemon Diamond or Pearl for the DS. The DS battle mode is the simplest, and in a way, it best exemplifies what Pokemon Battle Revolution is all about: making Pokemon fights look cool. Using their active Pokemon from Diamond or Pearl and the DS itself as the controller, two to four players can have a good old-fashioned Pokemon throw-down as big, polygonal versions of the pocket monsters go through the motions on the TV.
In addition to the local multiplayer options, Pokemon Battle Revolution can be played online against other players and is the first game for the Wii to hit the US with live online functionality. It's a no-frills affair where you can choose to battle randomly against other trainers or directly challenge any trainer with whom you've exchanged friend codes. The bummer here is that your friend code for Pokemon Battle Revolution is different from the friend code for the Wii itself. It's not too different from how the DS works online, and Nintendo has stated that it plans on assigning discrete friend codes for any Wii games that go online. So, it's not surprising, but it's still kind of a hassle.