What I Look For In A Roleplaying Game

First, I look for an agreeable setting. I want an escape; not a survival game. I struggle every day to survive in real life. Do I want starvation to be a possibility? Yes, but I'm an adventurer. My life is about survival and risk. Making sure I have food & water is second nature to me. If I am captured or somehow overcome, then it makes sense for basic necessities like food to become a concern. If I strike out into a desert when my normal travels are through areas where water is easily found, then I need to concern myself with provisions, but those are all special circumstances. I don't want such menial things to be a spotlight feature. I want adventure. Whether that's saving the fairy princesses, defending my homeland, saving the world, or standing for right in a difficult situation, I don't care, but I want good to prevail and be the focus of the setting, though not necessarily of every game session. That's why I don't enjoy Vampire or Dark Sun. They've been presented to me as back-stabbing, nitty-gritty, climb your way to the top & who cares who you step on enroute worlds. I don't enjoy that.

Granted, those settings can be run in the heroic manner I am trying for, but they don't lean toward such a style of play. I do enjoy the Realms. Yes, Toril has its dark side, but it's largely a world that is made up of good people. Are there evils to face? Aye, aplenty. But they don't dominate or rule everyone. The world isn't run by an evil Dark Lord. I'm more likely to be overcome by a wandering monster than become the focus of the Church of Cyric's ire. Can I make myself their target? Oh yes, but if I do, I'm doing so by butt-kicking for goodness.

So I want a sense of heroic in the setting, but on the flipside of that, I'm not looking for a world run by Paladins that follow the "Lawful Stupid" alignment. My every turn shouldn't be halted by some goody-two-shoes going "there's a law against that, citizen;" or "there's only one right way to do that - go through the proper channels or be imprisoned." I may encounter a town or village where that's the way things are run, but not all the time.

Again, the Realms provides that for me. That's what I look for in a Campaign Setting. What I look for in a rules set is detailed simplicity.I look at combat and  I look at skills.
I want to be able to be very good at a variety of things; not just a one-trick pony. Just because I'm a Mage shouldn't dictate that I can't be very good at Stealth. Just because I'm a Rogue shouldn't dictate that I'm not good at being a Charismatic, Bard-like character, capable of playing the crowd, but disappearing in an instant. Just because I'm a Fighter shouldn't mean that I'm a numbskull, incapable of sounding intelligent on anything but war and tactics. I want to be able to be that fighter that is the charmer, wooing at court, but a juggernaut on the battlefield. I don't want my perception and social skills tied to my race or class. Skills might be enhanced by Class or Race, but not limited.
Combat should provide for variety. It shouldn't be a "one roll is the end-all." If I'm making an overhand, finishing blow, it should be different from grabbing the foe by his throat. Marshall proficiency shouldn't be limited to Class, either. If I'm a mage, there's no reason I'm not practicing fencing to get away from the books for awhile. I'll never be as good as a master swordsman, but that's where my Art balances the equation.