Fun has less to do with individual gameplay elements than execution. The balance between weapon types makes a huge difference in FPS games. Chip damage vs recovery mechanics, cover systems vs stealth vs run and gun etc.
Similarly there have been so many health systems in FPS games you don’t need to invent something particularly new, but you do need to pick something appropriate to the gameplay. For example in PvE players need to be able to fight waves of enemies but in PvP games nobody wants to stand for 30 seconds firing at a bullet sponge.
Puzzle games need interesting puzzles, racing games need appropriate tracks, and so forth.