The only thing the game lacks from other versions is graphics.
The Good: Plenty of modes and content, good graphics and still has a good frame rate, Online play is very well done, tracks sound good, full character customization, DLC
The Bad: Graphics are not always great, 4 Wii remotes for full multiplayer experience, simplistic multiplayer, the game forces you to create a character right off the bat
Rock Band 2 is a great rhythm and music title for the Wii. The gameplay is simple, play the notes as they come down the screen. There are four modes of play: guitar, bass, drums, and vocals. There are many songs in the main set list of Rock Band 2, I think around 85. The songs can be unlocked by playing the campaign, or career mode. The career can be played as a single player or with multiplayer. There are many different venues in which you play and unlock these songs. Once you get them all, you can rock out in Quickplay.
The songs themselves sound great, and you will have tons of fun playing them, whether it is by yourself or with friends. You are not getting nerfed on sound quality; it's all there.
The graphics are great in most instances, but some things, like the drummer animations, are jerky and awkward looking. But they are, by the Wii's standards, good especially compared to other games of similar genres.
In character customization, you can choose from many different outfits for your character. And the clothes are even split into categories like "Metal clothes" "Punk clothes" and "Goth Clothes". So if you want your character to look a certain way, chances are you will find what you are looking for in the wide selection. The only problem with making your character is that it forces you to make it as soon as you start up the game for the first time. For players who just want to jump right in and play, this can be a little annoying.
The most exciting aspect of these kinds of games is the multiplayer. And Rock Band 2 does not fail to deliver in this category. The main campaign can be played with up to four players at once. And of course quickplay is a jump-right-in-and-play kind of thing for up to four players as well. You can also take your game online over Nintendo WFC and play with people from around the globe. Now some people are skeptical when it comes to the Wii's online, but in Rock Band 2 it is, simply put, superb. Finding a match is easy. Join in, choose your character, and find other players. It's that easy. When playing online you and the other players alternate picking songs to play. The online almost never lags, (unless there is a really bad connection from someone) and the frame rates hold up. All in all Rock Band 2 delivers a solid online experience.
There is one problem with the multiplayer, however. Really the only thing you can do is play with each other in a band, rather than face off against each other. It would have been nice if Rock Band had a Pro Face-Off type mode like in Guitar Hero where you and someone else play against each other to see who can get the best score.
So if you are trying to decide on a good music game to get on your Wii, I personally prefer Guitar Hero, but both games are worthy of checking out, so choose wisely, or get them both!