I understand cradle Catholic
as meaning still practicing, having been a practicing Catholic one's whole life. From baptism seems like it would actually be synonymous, since only people from non-Catholic families would be baptized later than infancy, thus becoming Catholic converts.
The contrasting term I'm most familiar with is lapsed Catholic,
meaning no longer actively participating. Recently in one of the papers I saw an editorial using fallen Catholic
in apparently the same sense, but that sounded awfully drastic, like someone who had committed a mortal sin or been excommunicated. People who have actively withdrawn their membership, like in Germany to avoid the tax, would just be former Catholics,
(OT: By the way, the writer had what sounded to me like a really good suggestion. Many US bishops tasked with administering the pope's survey seem to be giving the forms only to active current parish leaders -- that is, insiders. So reform groups are inviting any Catholics who weren't surveyed to make their voices heard by taking a shadow survey at http://www.surveymonkey.com/s/SynodOnFamilyUS
before Dec. 15. That sounded really worth doing to me, since the pope also needs to hear from Catholics who feel rejected or excluded.)
As for Protestants, I'm not actually familiar with 'cradle' in that sense so much as simply lifelong
(Lutheran, Methodist, Presbyterian, Episcopalian, etc.). Or even third-/fourth-/fifth-generation.