Resident Evil in a nutshell.
First off, let me get this out of the way. The Wii Zapper sucks. Trust me, it doesn't make the game any better. In fact, the way you're supposed to hold it is uncomfortable and it really puts a cramp on your hand. Besides, if you're just buying the Zapper to get that Zelda game that comes with it, it's not worth it. And that's coming from me, one of the biggest Zelda fans around.
Anyway, this game is basically Resident Evil in a nutshell. If you didn't have the time to play through all the other games in the series just to get what's going on with the story, this game sums it up pretty well. The levels are broken down to chapters, each chapter covering a different game. Each chapter is then broken down to three levels. Although I was a little sad when I found out that Resident Evil: Code Veronica and Resident Evil 4 weren't included, the game makes up for it by having two exclusive stories not featured in any of the games.
While the game isn't long compared to other RE games, (about 8 hours if you breeze right through it) it's a hell of a lot of fun. The controls are easy to pick up and the levels are modeled straight from the games, so you'll feel right at home when playing.
All in all, if you're a RE fan, or even a fan of light-gun games such as Time Crisis and House of the Dead, you'll love this game.