You could start here
Beatles: Rock Band
Green Day: Rock Band
LEGO Rock Band
Rock Band Unplugged
Rock Band Blitz
Rock Band Mobile
Rock Band iOS
Rock Band Reloaded
That one puzzle game they had on Facebook that was like a combination of Collapse and Bejeweled
I never liked how busy the overdrive note highways were on Beatles: Rock Band. Combine that with the opacity of the tracks and all the stuff that goes on behind them and it made for a very disorienting experience for me. Did that bother anybody else as much as it bothered me?
If I had to pick just one it would have to be Blitz with Lego in a close second.
Out of these options, The Beatles Rock Band is my pick. It was designed so wonderfully to match the band, and I loved the presence of real events/locations throughout the history of the band. It really gives you such an amazing sense of the band's progression. Not to mention, every detail was clearly very carefully and lovingly considered. That animated sequence at the beginning of the game is still one of the most beautiful things ever.
It's kind of a shame that after The Beatles, Green Day Rock Band ended up feeling like an afterthought. I'm not crazy about the band, but having only three "eras"/venues (two of which are from way later in the band's career) makes it seem like the game was rushed. It's unfortunate, because The Beatles:RB could have been a real argument for making a run of band-specific games... it's exactly how they should be done.
So, The Beatles is my favorite spin-off.
Blitz is really fun. I just wish there was more to it -- maybe different fictional Rock Highways to drive on or a local multiplayer mode or something (similar to what Frequency and Amplitude had). The arcadey gameplay is really engaging and it's a cool way to revisit one's RB library, but the atmosphere gets old too quickly. My favorite thing about Rock Band 2, 3, Beatles, Amplitude... these are all Harmonix games that feel like they take place in a colorful, lively world that you want to hang out in.
Blitz, unfortunately, takes place in a monotonous world. At the end of every song, you end up at that same theater, with that same blimp, with those same policemen, with that same cheering, with those same fireworks. I think I specifically have a problem with that screen. I always find myself wishing I could skip it, I've seen it so many times.
But hey, maybe that'll be something to address in Rock Band Blitz 2 in 2013?
Well, the word "best" is purely subjective but as an art form I feel The Beatles clearly excels over the other iterations of Rock Band and invites the player to share in an experience that no other rhythm game has made possible before. On the other hand, Lego Rock band provides such a customizable, happy-go-lucky fun time,
I'd be hard pressed to find another music game to draw comparisons with.
"War is over... if you want it"
- John Lennon