No, this is not a review of a cheesey Bruce Willis movie. Rather I refer to the "X Factor" which gives a game depth.
Most games have the four "M"s in common - Movement, Melee, Missiles, and Morale. It's quite possible (though I don't recommend it) to make a generic game engine for these areas and apply them to different eras. Heck, Games Workshop have been doing it for years. Legends of the Old West, Legends of the High Seas, and Lord of the Rings are practically the same game, and cover 1860s cowboys, pirates and medieval fantasy skirmish. WW2's Flames of War and Bolt Action bears some startling similarities to the sci fi giant Warhammer 40K and the Gruntz is obviously Warmachine in a sci fi skin.
However to make a game "stand out" I think you need a fifth element. It is that "something" that makes the game stand apart and adds another dimension to the gameplay, outside the usual Movement-Missile-Melee-Morale staples.
This post has absolutely nothing to do with the movie. Sorry, disappointed fans!
The obvious choice for fantasy and sci fi games, a good magic system adds a completely different dynamic to combat. In sci-fi, this is usually some form of "psy" powers. I think magic should not only be another form of missile or melee attack but offer more gameplay options. For example, the magic in Song of Blades and heroes offered only a "fireball" (aka missile) or a "freeze" attack. That's pretty limiting and uninteresting. On the other hand, magic should compliment the other elements of movement, melee, missile etc and not overwhelm it. It's the "fifth element" not the "only element" of gameplay. (I remember friends whinging about certain edition of WHFB which they labelled "Magichammer" as whoever brought the best wizard tended to win). I'd probably favour a magic "minigame" with risk v reward where you have to manage magical resources. Which brings me to another option:
Malifaux utilises a card deck which you use for combat. You can keep a "hand" of 5 cards which you can use to boost your attacks. Managing your "hand" adds depth to gameplay - a player who makes poor movement and combat decisions might be able to save himself through clever management of his "hand" - but using his good cards to extricate himself from trouble will leave him vulnerable later.
"Command Points" can be used, which can be spent to allow extra actions or boost actions with dice modifiers are also common - for example in the DP9 mecha games Lightning Strike and Heavy Gear.
Infinity gives players an "activation pool" of counters equal to the number of troops, but allows a player to use the activations any way he chooses. I.e. a player with 8 miniatures has 8 activations, but can could choose to spend all of them on a single figure (i.e. one mini activates 8 times in a row) or any combination, up to the total of 8 activations. Choosing how to manage your activations adds a lot of depth to gameplay. Games like Battlefield: Miniature Modern Warfare and Mayhem take this further by using the same activation "resource pool" idea and penalizing additional activations by the same unit.
A "dice pool" as seen in games like Confrontation, Ronin and Bushido can make melee interesting. In the Conan-eque CROM rules, all actions and movement are governed by the "dice pool" and you can "burn" a dice for a guaranteed success.
The pulpy Conan-esque CROM rules by Matakishi (his website is a fantastic source of wargame inspiration) use a "dice pool" which adds resource management to every action you take
This is often overlooked. The activation method or initiative system for moving models is often an afterthought in game mechanics. A simple IGOUGO or even an "alternate move" system is equitable method, but completely sacrifices interesting gameplay potential.
The obvious contenders are "reaction" systems like those in Infinity and Tomorrow's War, but it could be as simple as what I call "evil alternate move" - you can choose to activate one of your own units, or force an opponent to activate one of theirs!
There's also the "risk vs reward" system of Song of Blades where you can roll dice to act with a model - more dice means more potential actions, but more risk of failing and passing the turn to the opponent. GW's Warmaster (and I think Black Powder?) used a similar system - being able to activate units in sequence until a leadership roll is failed makes for interesting risk vs reward decisions.
Activation can be combined with the "resource management" such as in Infinity. The activation/initiative portion of most games have huge potential, as games rarely push beyond the "IGOUGO" or "alternate unit activation" envelope. Making this part of the game exciting and interesting will make the game stand out compared to others.
Potentially clever "command and control" rules could fit in this category but since I avoid games with written orders (laboriously writing stuff down just doesn't "gel" with my usual modus operandi of pushing models around making pew-pew noises) and ancients and Napoleanics where command and control systems seem common (I find both periods rather bland and cliche, heretic that I am) I don't have a lot of comment to make in this area.
I liked how in Battlefleet Gothic ships or squadrons could (if they passed a leadership test) be given "orders" to boost their speed, agility, defence or firepower. It was the "X Factor" which made me enjoy a game that was essentially WW1 naval combat for goths.
Set-Up... and other things
This is an area I had never previously considered until I tried Chain of Command. The "setup" phase of most wargames usually consists of one side choosing to go first or choosing their table edge and then deploying 12" (or some other predetermined distance) from said table edge.
Chain of Command has a very neat mini-game in which deployment area for troops is determined by maneuvering counters around the tabletop until they are "locked" in place by an enemy counter which comes within range. The position of the counters once they are all "locked" in place then determines potential deployment zones for your troops. This means deployment is very "organic" and avoids "gamesmanship" where you set up deliberately to counter a particular enemy unit, such as placing your anti-tank guns on a hill directly opposite his tanks. (In an extreme example, I remember a 40K game where one guy spaced his forces out so his enemy (who had only drop-capable troops) had nowhere to "drop" his troops and therefore had to forfeit the game.)
Anyway, kudos to the Two Fat Lardies for this idea, as deployment is given even less consideration than activation and initiative in most rules.
So - what things give a game "zing" for you - what is the "X factor" or "fifth element" that makes a game stand out beyond the "usual" Movement-Missile-Melee-Morale mechanics?