The 2 game systems I currently run are pretty much on opposite ends of the spectrum in terms of fair play (PF2e and CoC). For PF2e the math of the system and how encounters are constructed typically means you can expect a fair fight each time you roll initiative. Some character options can be better situationally, but for the most part character options are balanced which means the fights are typically decided by decisions made by the players and a fair fight can be expected. CoC on the other hand is not about fair play at all. The players know combat is lethal and not all encounters are meant to be solvable through force, so it's up to them to decide which encounters to avoid.TL: DR Folks are drawn into RPGs by system mastery and/or the concept of a fair match. Some lean heavily on one or the other. How about you?
As far as system mastery my preference is games to not require a high level of system mastery to be played. For players in the games I'm in I like seeing people developing their characters based on events that occur ingame and not based on what gives them the best options to win. In my first 5e campaign with my current group, the group at 2nd level was ambushed by a white dragon terrorizing the region they were in. One of the players decided their character was scarred by the experience and took the Alert feat so they wouldn't be surprised again. They also roleplayed their character as nervous and constantly on the lookout for danger. In the first session of PF2e, another player's character tried to climb down a cliff and fell which almost killed them. When they leveled and could take a skill feat, they chose Cat Fall after saying their character had been practicing tumbling since they had their big fall. That character became a little more daring when it was time to climb things because they had been practicing. To me that's what makes roleplaying games fun.