A very simple real world example of a song that, while not difficult in Rock Band, is a much more difficult chart than in real life.
About 40 seconds in, it hits the chorus riff. Not too tough, but your fingers are doing a lot of chords and they move quickly. On a real guitar, this is in drop-D and you can play the whole thing with just a one finger per chord. It's very easy, even for beginners to learn. This is much harder.
Any song that is based on acoustic fingerpicking is also usually more difficult in Rock Band.
I hate the superiority complex people get about real guitar vs. Rock Band guitar. I play both, enjoy both, and both are different. Looking down on Rock Band or Guitar Hero as "not real guitar" is like scoffing at Call of Duty because it's "not real killing people."
Anyway, the only thing missing in my life is Pink Floyd: Rock Band or equivalent DLC. If you think such a game would be boring, it is you, sir, who are boring.