The Flaming Lips I view as sort of an updated 60s / 70s era psychedelic band, guys who missed the hippie generation but love the hippie vibe. They have two albums that are absolute home runs (Soft Bulletin and Yoshimi) and a lot of middling stuff.

But to my ears they sound nothing like Radiohead, nor are they trying to do the same thing. Radiohead makes music that is jarring but still beautiful. They peaked during their OK Computer to In Rainbows stretch, although I still enjoy their more recent albums. But their music is fundamentally pessimistic and brooding while the Flaming Lips at their core are cheerfully optimistic.