I have played a load of different games from FPS, RPG's down to Strategy games... but I always find myself coming back to Combat Flight Sims, IMHO the reason for this is that the genre makes you learn the ins and outs of each aircraft to truly master it no other games requires you to get so involved with getting to grips with the basics before you ever fire a weapon in anger... its not just mindless button smashing that I find most ever games boil down to when you are in a tricky situation.
This allows you to show off your skills/what you have learnt in a way that no other game truly allows, sure FPS's allow you to show how quick your reactions are and strategy games allow you to show a great deal of cunning (until you opponents stumbles on your massed up hidden troops or you find he has built a virtually unimpenetrable fortress
), flying is not just about learning your aircraft its about situation awareness, knowing when to fight and when to run... no other game genre except some exceptional RPG's and the occasional "once in a blue moon" well written FPS's games have grabbed me in a similar way.
So what is it for you, what brings you crawling back to the most under rated and, in comparison to others, unpopular genres out there?
Oh all that and my undying love for anything that has wings