My take:
If you plan to accumulate most of your points through hotel stays, then you have a number of good options - as noted in the insideflyer article mentioned earlier in this thread; they especially liked hhonors, choice, and wyndhem (I agree re hhonors)

But if you will be getting your hotel points through credit card spending, SPG is the best choice. With their CC You get 1 point for $1. hhonors gives you between 3-5, MR 1 (with their premier visa you can earn 2 on airline, dining, car rental), priority gives you 1 per $1.
But 1 starpoint = about 5 points in the other programs (a rough estimation, but still fairly accurate)

For example: to use Marriot own comparison (meant to show the benefit of their program:
http://www.marriott.com/marriott.mi?page=beherefaster

Here You would need $130,000 in CC spending to reach that reward with MR ($280 grand with PC), $72,000 with SPG.