RE: Hydrox are back!! (?)
PLB is right. Hydrox was an ADULT cookie, with a taste more cocoa than chocolate and with a less sweet filling that Oreo's vanilla-flavored lard.
Unfortunately Oreo went with the philosophy espoused by the Vatican, the Nazis, and MacDonald's, "Give me the children and I'll give you the next thousand years." Hydrox consumers, being adults, got old and died. Oreo consumers, being children, grew up indoctrinated into buying only Oreos and passed this on to their children.
I look forward to buying a stash of Hydrox!