The Rock Power Challenges in that game take The Power of Rock to an all new level, which includes destroying a building, chasing away ghosts (While playing the Ghostbusters theme of course), and using it to defeat a octopus.
At the end of the Endless Setlist 2, the game tells you to keep playing your instrument after you have beaten Painkiller. If you do, then fireworks will shoot off in accordance to your playing, making an already awesome accomplishment even moreso.
Speaking of Bohemian Rhapsody, it will have vocal harmonies and keyboard charted separately from guitar. Combine this with "Pro" Mode and you could not get a truer rendition of this awesome song in a Rhythm Game.
The Rock Band Network. So now anyone can put songs in the game? Difficult, but with (almost) the same potential quality as the original songs? Harmonix wins the Internet.
However, not only can they be pulled at any time for any reason, RBN songs cannot have Pro Guitar charts (at least, not for 6 months after Rock Band 3's release ever). And the X360 gets first (and frequently, only) dibs on the songs.
"Science Genius Girl" by Freezepop and "Funk #49" by James Gang are frequently cited as the most fun songs in the game to play on drums. Also, most songs drummed by Keith Moon (The Who) or Mitch Mitchell (The Jimi Hendrix Experience).
For Bassists, most songs involve strumming long strings of the same note. For "Won't Get Fooled Again", however, the bulk of the song involves long strings of notes that scale up and down the whole board. It's a blast to play on Hard or Expert Bass, provided your left hand is up to the challenge.
In addition to its excellent drumming part, Funk #49 is also considered one of the top bass songs. "Hysteria" by Muse and "Typical" by Mutemath are often cited as two other top examples.
Bassists will also often quote Rush's songs, especially "YYZ" (which has a bassline that's arguably harder than the guitar part) and "Red Barchetta" (which gives the bassist a couple short solos.) And now there is their new song "Caravans" which has lots of chords and two marked solos.
Most guitarists will point you towards many of Stevie Ray Vaughan's songs, particularly "Lenny" and "Texas Flood". Other popular songs include the Allman Brothers Band's "Blue Sky", Freezepop's "Get Ready 2 Rokk", and the live version of Thin Lizzy's "Cowboy Song"
Most punk songs are loads of fun on Expert Guitar, due to being based mainly on rhythmic altstrumming. Anything by The Offspring or Flogging Molly's "Drunken Lullibies".
For vocals, you have pretty much anything by Queen, but especially "I Want It All," "Somebody to Love" and RB 3's "Bohemian Rhapsody." Other excellent vocals songs include Iron Maiden's "Fear of the Dark," Pearl Jam's "Jeremy," Journey's "Don't Stop Believin'" (duh) and, courtesy of RBN, Stan Bush's "The Touch." RB 3 added a lot of excellent vox songs to the mix, like Whitesnake's "Here I Go Again" and Dio's "Rainbow in the Dark." Basically, if you like singing, there is a LOT of good stuff in Rock Band.
2009 added SpongeBob SquarePants songs of all things to the DLC list. Sadly the theme song isn't there...