A solid collection of an old arcade favorite. At least worth a rental if you're apprehensive.
Now that I've bought this game, I feel qualified to review it through my own play through of it.
Metal Slug has been an arcade staple for a long time and its not hard to see why. It's frenetic shooting arcade action at it's finest. Simple as that. I have a hard time thinking of a series of shooters on the arcade that stack up to the humor and general fun of these games.
That being said, this game isn't perfect. First of all, play this with a friend because it's more fun. It just isn't the same thing when you're alone. The game is an arcade emulation. This means that you can have infinite continues. While this doesn't mean the game isn't challenging, it does show the limitations of the arcade. To a certain extent, you could just run from left to right pressing the fire button and go through the game fairly easily. But this would demean what the game is truly about, and if you want a challenge, you can shut off the continues, but the balancing end means that the game becomes quite a bit harder without continues. The load times are a little odd considering the age of the games and the Wii's capabilities. They aren't completely jarring or anything, I just find them a little unnecessary, but then again, it was one of the launch titles for the Wii and I guess I can't condemn it entirely for that reason.
Do not play this game with a Wii-mote. It just doesn't work. Go out and buy a Gamecube controller or borrow one because it just works better in every way, much like Smash Bros. Brawl works better with a GC controller.
If you value fast paced shooters with plenty of personality and history, pick up this game. It's a lot of fun a great time with 2 players. (Just make sure you have GC controllers.)