Even thought they're meant to be a vent for ideas which don't fit in a collaborative effort, or whatever other reasons there are for wanting to make music that will not fly under the name which an artist is most famed for, there are instances where these supposed distractions end up better than the day job.
Menomena were originally a side-project of Lackthereof, the solo project from their drummer Danny, before it became clearer that not only did Menomena have wider appeal, they were a hell of a lot better too.
Brad, who contain Pearl Jam guitarist Stone Gossard, have created some incredible music. Though to say that Stone is pivotal to their sound is questionable. If anything, it's just a way of him lending his credence to Shawn Smith whose material with Satchel show just how little Stone changed things.
I'd never say 13 & God are better than The Notwist, but second to For Hero: For Fool, both of their albums rank as my second and third favourite that Dose One has been involved in.
Any crazies like Atoms For Peace more than Radiohead?
Are there some side projects that are so bad that they sully the way you view the original band? Maybe they reveal their songwriting process in a more clumsy way taking the magic away from the original?