all games are beatable if done correctly.
blackjack for instance, can be beaten by cardcounting. if the casinos catch u cardcounting they will ban you.
however, card counting is not illegal and a court of rule has ruled it is legitimate. If you would like there is more info here http://www.sydneycasino.info/
casinos win because most players dont use winning ssytems, and the losing plays easily cover the few who actually takle the time and effort of running them.