Password seems simple to do on the surface, but I'd think there's the searching for words that play well on TV, and figuring out whether they can be stretched out for ten descriptions, or simply two. If the latter, you have potentially boring television.
Wheel puzzles also seem simple enough, even more so until about the mid-90s, when the producers started adding gratuitous extra words and calling routine (read: mundane) stuff an "Event"*. I've said before that Vanna's first puzzle, "GENERAL HOSPITAL", would now be "EMMY AWARD WINNING SOAP GENERAL HOSPITAL", so I think finding a way to get a challenging enough descriptor makes things a little more difficult, even if they do serve as clues to the puzzle.
Honestly, I would think most word games are still going to be difficult to write for. Throwing a bunch of random words or names together doesn't mean the job is easy. I remember writing words for someone's Pyramid game years ago...cobbling seven of a particular anything that are also easy to describe is tough. Same goes for six good Winner's Circle categories.
I imagine Deal or No Deal couldn't have been too difficult. :-P
/*Calling it "What Are You Doing?" doesn't make it any less silly