It's simply a matter of what one point buys you in its native form. "One point" by itself means nothing.

I look at it like this: if I didn't have any hotel points, what type of hotel would I pay for for a leisure stay and how much would I pay for it? Then, in each of the major hotel programs, I can see what Category that type of property is and how many points it takes to get a free night. For everybody it is different: if you ordinarily Priceline 2-star hotels, then hotel points will never be worth much to you. If you ordinarily pay top-dollar for European Starwoods, then they will be worth a lot.

The way I use them, a Starpoint is worth about 3 cents, a Marriott point is about 1 cent, and an HHonors point is about .75 cents. The way you plan to use 'em may vary a little or a lot.

This ratio - 1:3:4 - also passes the smell test when you look at a Diner's Club exchange chart. If you figure they are allowing exchange somewhat based on how much it costs them to buy the points, then it generally makes sense.

Of course, we FT'ers know that there are optimal ways to milk value out of points/miles.

Edited to add: there are a bunch of Milesbuzz threads about value of miles/points. There are also a lot of thread about the best credit cards. Many, many FT'ers speak highly of SPG Amex, but if you read the CC boards you'll find HH Amex fans, Diner's Club fans, and fans of certain cash-rebate cards. You have to figure out what works best for you.