[Darekun]

To me, "campaign in a box" implies something like D&D's setting books and boxed sets; you get the rules and genre assumptions in the PHB+DMG, but the Dragonlance book(say) gives you maps, settlements, cultures, races and monsters, seeds and hooks, etc. A GM with a general familiarity with the material can pick a town off the map, walk newbie players through creation, pick a hook from a later chapter, and go. The GURPS equivalent would be the setting books(Prime Directive, Alpha Centauri, THS, etc).

Basic+DF, OTOH, gives you the equivalent of PHB+DMG. It's got enough setting assumptions to proceed without picking a specific setting(like D&D gives you Greyhawk), but the town, the inn, the innkeeper, and the dungeon the GM will have to wing, unless they add specific materials to pin that down.

Likewise, MH could be Black Ops or it could be Buffy. There's probably enough assumptions to proceed without picking a specific setting, and you can add specific materials to pin that down.