Before spending too much time drooling over perks, the OP may want to have a long, realistic look at where he is likely to stay to earn those points (or if the bulk of the points will come from credit card spend), and where he would want to redeem those points. Look at it from both a location perspective, and a budget perspective.

GHA (Global Hotels Alliance, http://www.gha.com) has some lovely"experience perks" like free wine tastings, walking tours (like foodie tours or chocolate tours, not the boring beaten path tours), chef's table dinners and so forth. That's on top of room upgrades, To me, those seem like the "best" perks around-- free or cheap stuff that really adds a lot to my trip. But with their small portfolio of brands and limited presence in the US, I'm not likely to ever actually enjoy those perks.

Truly the "best" program is one you actually get a lot of use out of, and since higher status usually gives more abundant benefits, the best program is also the one in which you hold (or can reach) the higher status. Once you determine where your hotel points will come from (USA, Europe, credit card, budget hotel, luxury hotel, I'm paying, work is paying, etc) you should have eliminated at least some of the major programs. Then you can compare the rest to eachother and see which you think will be most valuable to you.