The original Fawcett comics Captain Marvel is definitely ligne claire- down to most of the covers. There is also more than a touch of Tintin in Billy Batson - so much so that I can pretty easily do an amalgam- Tintin Batson who when he utters the magic word CHANG! transforms into the superhuman Captain Marvel- a superhuman bluff sea captain. :) But back to the more serious article.
Captain Marvel had much the same sensibility as Tintin too- innocent orphan boy reporter hero, whimsy, some full blown elements of fantasy - super intelligent Snowy is more than matched by hepcat Tawky Tawny for example.
It's the ligne claire flaire that's been missing ever since too. It will take more than loony tunes officianado Jeff Parker to create a true modern Captain Marvel. Personally I'd hand it over to either the Rainbow Orchid or the Tazo the Public Servant guys.