What makes a casino game hard to play?
The most important contributing factor to that decision has to be the complexity of the game, either in terms of the rules or in the computed probabilities. There is a certain minimal amount of skill involved in playing even the simplest casino game, although that skill only involves managing the money with which you gamble.
Here's an example:
A slot machine pays higher prizes for maximum bets than minimum bets, but if the probabilities of your spinning up some sort of winning combination are the same for both extremes of the betting spectrum are the same then your money lasts longer if you make smaller bets.
While this is true of many gambling games it is not necessarily so with all of them. For example, in Poker you may be forced to increase your bets with other players just to stay in the game. In Keno the more numbers you bet on the worse your chances of winning a prize. And some slot machine games require that you bet above the minimum amount in order to win certain prizes, such as their progressive jackpots.
If deciding which games are the hardest were simply a matter of knowing what the odds and probabilities are, gambling would be much simpler than it is. But many people don't realize they are playing games with unknown factors. The terminology is confusing, too. Take "odds" and "probabilities" as an example. Most of use these words interchangeably but there is a technical difference and the odds are never same as the probabilities.
The "odds" are the ratios of prizes to bets. You can see this most easily on the roulette tables. If you bet on a single number the odds are 35 to 1. That means you'll be paid 35 dollars for every dollar you bet if your number comes in. But the probability of that happening is 1-in-36 on a single zero roulette wheel and 1-in-37 on a double-zero roulette wheel. The difference between the odds and the probabilities is called the "House Edge". It's about what the casino keeps over time from all player wagers.
Slot machines are programmed to pay back a certain percentage of bets to players over time. This is called Return to Player. It varies from about 60% to about 98%. Some casinos tell you what the theoretical return to player is. Many casinos don't. So when you head to the slot machines, you may be about to hand 40% of your money to the casino. The rule of thumb is that the more competitive a given casino's market, the "looser" its slot machines tend to be. It's not easy for the casinos to change these settings so they maintain consistent RTPs over time.
Variance is another factor you are not told about, although it's possible to compute them. The variance is a statistical measurement how likely you are to win more money than you bet. On games with large jackpots the variance is high, which means those big prizes are not awarded very often in a given period of time. Put another way, in a 90-day period a low-variance game should pay its maximum prize more often than a high-variance game.
If you don't know the theoretical Return to Player, the Variance, or the Odds-versus-Probabilities of a game, you are playing under the hardest possible conditions.
Remember the old adage, if it sounds too good to be true it probably is. Keno is considered to be the worst of all casino games, along with any other lottery games that work like Keno. In fact, you have a better chance of winning a million dollars on slot machines than you do on your state lottery tickets. But Keno is not all that bad if you just play the minimum numbers. You are more likely to win and you risk the least amount of money. But your prizes are lower. That variability or player discretion makes Keno a better gambling game than your state lottery.
The rule of thumb here is the bigger the jackpot the less likely you are to win it. But they want you to think about what you would do with all that money, not what you are doing with the money you have.
Chuck-a-Luck is another game that is exciting. The game mechanics are much simpler than Keno and the jackpots are much lower, so you must have better chances of winning, right? Chuck-a-Luck is based on the ancient Chinese game of Sic Bo. Both games entail betting on the face up numbers that result from rolling three dice (the casino controls and rolls the dice). There are many betting combinations in these games.
The rule of thumb with these games is similar to that with roulette: the lower the odds the better the probability that you will win. Low odds = low payoff.
To overcome the sluggishness of building up riches with low odds, players compensate by betting more money. This almost always works in the casino's favor because the casino has more money than you and it limits how much you can bet. Hence, popular betting systems like the Martingale System eventually run into a wall: you either go broke or you cannot bet enough to recover what you have lost.
Most people prefer to play slot machines rather than sit down at a poker table because you don't have to think much with a slot machine. In poker you are competing against every other person at the table. High stakes poker can be pretty exciting but most of us would not last long against even middle-class professional players unless the cards just magically fell our way in every hand. Even then the other guy might bluff you into folding.
We feel better when we can root for each other and everyone can win on the same random play. That is what makes gambling fun for all and takes some of the challenge out of the games.