This next sentence could be a complete falsehood: the majority of people who play roleplaying games either find their ideal system or they leave the hobby. It seems true to me, but that doesn't necessarily make it so. In my high school, when I began roleplaying, there was a rather large crowd of people interested in P&P gaming and we played a wide variety of systems: various editions of D&D, Werewolf, Vampire: The Masquerade, Mage, Big Eyes Small Mouth, Shadowrun, etc. I don't live around the area anymore, but, from what I can tell, a lot of those people don't play games anymore. Those who do pretty much play whatever system they have the most books for, or whatever is most nostalgic for them.
Maybe I have some genetic disorder where I'm predisposed to wanting to see what hue of grass is on the other side of the metaphorical fence, but I'm always looking at new systems. I've become pretty good at finding ones that fit particular needs but I've yet to find the one. This is not a quest for perfection; rather, the ideal system for me and my players.
Without getting into semantics, let's define the ideal system as one that serves my purposes best. These change depending on the type of game I want to play. The Burning Wheel game I'm running right now is intensely story driven. There's plenty of action, too, but each fight, due to the nature of the system, means a whole lot more as combat is so lethal. The players have to want to risk death and seem to do so only if it means accomplishing their goals. This is, bar none, the best ruleset I've found for any fantasy game where the focus is going to be on roleplaying. The Duel of Wits rules function like a social combat for negotiating conflict; players write beliefs as part of character creation and are rewarded for testing them in play; the lifepath system creates fully-formed personalities from which to easily build back stories.
It is everything I want for a campaign that will have a narrative focus. Should I want to do a dungeon crawler-style campaign or something flavored closer to high fantasy, it would be a poor choice. It's not that the rules couldn't handle those types of games; it's just not well suited for it. The mantra-like response I get to this idea is that the type of game is determined by the players, not the system. I feel like this is one of those nature/nurture arguments. Both are important, but to say one trumps the other is conjecture.
I've yet to find my ideal system for dungeon crawling campaigns. I've never played 1st or 2nd edition D&D, but 3.X and Pathfinder are definitely not those systems. At low levels, it's hard to see why, but anyone who has taken characters over level 10 can attest to the exercise in tedium that combat becomes and anyone who has DMed high-level is well-aware of the amount of prep work it takes to hold this game together.
I'm holding out for Dungeon Crawl Classics RPG, but I am skeptical. Without a doubt, it's going to replace Pathfinder for most of my high-fantasy needs, but I hesitate to say that it will be ideal. I hope I'm wrong.
And there is the other, larger issue at the core of this post: does a RPG system exist which handles RP-intense campaigns and combat-heavy games with equal grace and measure?