As others have said there is no surefire best hotel loyalty program. Your first consideration should be where you typically travel and what kinds of hotels are available. For me personally, Hyatt is the best choice. Here's why.
-I LOVE their hotels. Even their lower end Hyatt Place is spectacular! Maybe Hilton would give me more frequent reward nights because their Hampton Inns and Garden Inns are in just about every town, but I'd much rather earn stays in a Hyatt than in a Hilton.
-Great Credit Card. The Chase Hyatt card has no foreign transaction fee, comes with two nights in ANY Hyatt as a welcome gift and gives me a free night every year I renew the card. I also get immediate Platinum Status by holding the credit card.
Like I said though, the tradeoff with Hyatt is that they are less prevalent. The Hyatt places are still only found in medium to large cities. So it really comes down to your travel needs. If you are frequently in small towns then Hilton or Marriott may be your best bet.