There is no universal system amongst online casinos about how all the various games are weighted.
Traditionally you were required to play through your bonus 30 times before you could cash out according to a table of weightings. So for example if you played only the slots you would had to bet the bonus amount 30 times because this already has a high house edge (typically between 4 to 5 per cent). And if you opted to play a game with a much lower house edge, such as craps or baccarat, you would have had to wager the bonus 300 times since these already had a much lower house edge. In other words, in the past at least games are weighted according to how quickly you are expected to lose the bonus and as calculated so that you lost your bonus at a quicker rate than it became cashable. The traditional way has now been modified by many casinos. Obviously to increase your chances of winning, you are betting off choosing to play the games that are weighted to have better payouts provided you know how to play those games. For example, blackjack offers great odds provided you know how to play blackjack which is a tricky game of skill. I still believe that you can’t go past baccarat as its so simple (once you rule some of the admittedly confusing rules) and has one of the lowest house edges of all casino games.