The question of an ideal LARP came up on Facebook, and after I had typed out my answer, I realized it was a bit too unwieldy as a comment. So my answer is here - what would go into making my LARP experience superb.
1) Genre would not matter much. I tend to prefer dark fantasy or horror games - but if this is going to be my ideal game, then the players, rules, setting and plot are all going to be so awesome I won't care much about the genre.
2) Combat will resolve relatively quickly. I don't have much of a mechanical preference - but I've been stuck in more than one MET mass combat, where it took everyone three hours to determine three rounds of combat. None of that in my ideal game. However combat resolves, it will be quick, easy and one of the more exciting aspects of the game. This would imply a boffer style mechanic, where initiative and rounds all come down to how long it takes the player to actually swing a sword or fire an arrow. However, I'm open to a different theater-style mechanic - Houses of the Blooded, for instance, makes use of a ritualized system of combat which relies on player negotiation and expending Style points. Alternatively, this could simply be a game written to be low combat on purpose - I could enjoy an MET game where the Storyteller wrote plot to lead away from mass combat; or allowed those combats to resolve in a quick, cinematic way.
3) My character should constantly be at risk. I should have a pervasive sense of what happens if I and my allies fail at our goals, and they should not be good. And not just death - my character should fear shame, exile, insanity, impoverishment, guilt or some other negative outcome. This shouldn't be a foregone conclusion (unless I'm playing in a Call of Cthulhu game), nor should it even be a likely one. But I enjoy feeling as if there are dire, painful consequences if my character makes a grievous mistake. Not only is it good motivation, but a potential opportunity for rich roleplay should those consequences occur. And if my character does die, I want there to be a way to quickly get re-integrated back into the game, even if only as an NPC.
4) This might seem a contradiction to the above statement, but I have found I prefer games with low PvP. I don't want PvP to be completely off the table, but I would like it to be infrequent. So far, the best way I've found to deal with PvP is to insist that players must come to a mutual understanding if they are at odds to the point of one PC contemplating the murder of another. I would rather spend more of my time trying to outwit and outfight NPCs and the plot presented by the game's staff than wondering if my supposed allies are going to stab me in the back. I should mention this attitude focuses solely on character death. Characters should feel free to pursue conflict and even impede each other's goals short of character death. But I have found that most games in which PvP is explicitly allowed and perhaps even encouraged, the game quickly becomes an arms race.
5) I would like my character to feel effective at what she has been created to do. Even if my character is weak at creation, I should be able to look forward to a time in which I have the capability of affecting the metaplot of the game. So far, it seems as though XP caps are the best way to create this - characters retire after about two to three years of consistent play.
6) A fair and creative Plot Staff. Every player will get roughly the same amount of attention, and egregious cheating will be swiftly and harshly disciplined. Nothing ruins the fun for me faster than being the victim of cheating which goes unpunished. A close second is being consistently ignored by the Storytellers (I once tried for six months to get involved in a particular storyline with zero success - I don't play in that game anymore). Players follow the example set by the Plot Staff, and so an energetic and enthusiastic staff will set the tone for the entire game.
7) An immersive game site. I don't require exceptionally high production values, but I'd like to see some effort go towards props and setting. I've found that having props and NPCs in costume helps me feel more in character, helps my fellow players feel more in character and contributes to the general immersive quality of the game.
8) A rule system which I can pick up within about fifteen to twenty minutes of reading the book. In an ideal game system, I should only have to refer to my character sheet a few times per game, and my character sheet should not take up more than two sheets of regular printer paper (i.e., I should be able to easily tuck it away in a pouch or pocket). If I'm expected to do math in my head, it should be simple and quick (subtracting hits from my armor is fine; having to compute several different numbers in my head at the same time is not).
9) A player base comprised of friends, who get into character and rarely, if ever, go OOC when game time is on. I want the player base to be committed to costumes and props - no tags that read "Suit, Crafts x5" on someone wearing jeans and a dirty t-shirt. I want to feel like I'm hanging out with my friends while I'm at a game, even if we're spending all our time in character. I'd also like the player base to be helpful to Staff - games in which everyone pitches in seem to be more fun than games where players only give a minimal effort to helping keep the game alive.
And that's my ideal game. Fortunately, I'm lucky to be playing in a game which meets most, if not all, of the above standards - a heroic fantasy boffer LARP called Dying Kingdoms. My character's home city was completely sacked at the last game, and she's due to retire from play soon. I'm already excited for my next PC.