I suspect a lot of game shows would be way more fun to participate in than to watch. There are exceptions: There was one called Match Game, in which celebrities would hear a sentence, then fill out the last word--usually with something from the gutters of their minds. It was fun to watch because they picked people with fast minds who were fun to listen to.
As for why we watch them ... I just don't know. Sometimes it seems like there's a horrified fascination.
Well, yeah... especially the part where you win the money would be more fun if you do it yourself, rather than watching someone else win. :)
But if the questions are a bit interesting its already a good start. Something better than "Which Rapper published the album XYZ in 2004?"
And yes, there is this factor of "will they make it?", especially also in Cash Cab. I guess we all have a certain perception when we see people the first time, and we make assumptions about their personality, intelligence ect. I guess thats also part of it.
When it comes to interesting questions, there's always Jeopardy!