Your point is well taken, Gordon. I have had the same reaction to the tendency of casual games to be repetitious clones with the same corny plots. I've posted some acerbic comments and parodies to that regard, but I do enjoy these little games for filling in the corners of my game-playing. Still, after playing a few in a row, I have to take a break. ha ha
It is hard to think of any casual games that would be considered truly "original," and take place in a recognizable, contemporary world instead of a hyper-colored fantasyland filled with green or lavendar smoke. The
Dana Knightstone series is more adventure-like than most casuals. And there is
Dire Grove: Sacred Grove, too. The
Adam Wolfe suggestion already made has merit, but it has a supernatural theme.
A few other casual games that come to mind, that aren't quite as formulaic or HO-heavy as some of the mainstream casuals, are the following. Some have no HO scenes at all and nary a witch or vampire to be seen.

Maybe check out a few Demos and see if these hit your sweet spot.
Eternal Journey: New Atlantis
Forbidden Secrets: Alien Town
Nearwood
Shiver: Moonlit Grove
Twilight Phenomenon: City of Cyan