IHG all the way, baby! Free night every year more than covers the $49 annual fee, which is imposed after the first year and the first free night. Then their Points Breaks program is sometimes unbelievable. (5k points per night at selected hotels worldwide.) Best of all is the Points + Cash Program with nefariously circumvents all the taxes, including those crazy tourism fees levied on unsuspecting travelers. No blackout dates, free upgrades, what's not to like?
Awesome hack: the free nights overlap around the holidays. DH and I each have a card. Every other year, we can get a "free" four-night stay anywhere. We've only done this once, but it was a blast!