BlondeBombers' StarAlliance ff-program comparison charts can help you in your decision making (there is no one general best, but their is probably one best for your individual flight patterns: what kind of paid ticket (class), from where to where to you fly, what is your award target (upgrades, free flights, for yourself or people flying together with you, status expiry dates, requalification rules, etc. etc.).

http://members.shaw.ca/deercroft/starall02.html