Each casino game has a so-called RTP (return to player), which describes the statistical percentage of collected bets that gets paid out as wins to player. The higher the RTP, the better the mathematics of the game. European roulette, for example, has an RTP of 97.3%. Slots have an RTP of roughly 96% on average, but individual slot machines can range from below 90% to over 98%, so the choice of a slot machine matters a lot. Blackjack can have an RTP of roughly 99.5%, but to achieve this level, you need to make good decisions. If you don't, your expected return will decrease significantly.