This is about as close as you are going to get from me in a "Grand Theory of Roleplaying". It's pretty simple really. When you boil RPGs down to the primary elements of what makes games fun there are 4 primary 'things' you seem to be doing over and over again. You could call them the 4 Modalities of Play, but I'll simplify it and just call them the Big 4.
They are "Those who Fight", "Those who Talk", "Those who Make", and "Those who Take." That's it. 4 big things everyone seem to be doing, 4 methods in which we interact with the various game worlds. 4 ways mechanically games are built.
Fight is combat, Talk to social interaction, Take is a wide range of stealing, rogue dirty tricks, and general covert action, and Make is kingdom building, crafting of items, and personal growth over external crisis.
The catch is a lot of games focus on 1 or 2 elements over all the rest, and that's fine. It's actually some of the elements that made classic games so good. A good game caters to all 4 elements, but folds the other styles of play into the primary one bolstering it. So D&D is more a Fight/Take game but folds Make into magic items, and Talk into things like Charisma checks and dealing with undead for some reason. (Thanks to the Van Helsing like Clerics no doubt.) Or Vampire both cWOD and nWOD which are basically Talk/Make games where you deal with politics and Empire building but Take/Fighting revolves around how Vampires hunt humans and each other.
Let me give you some icon examples:
Those who Fight - Very few games stand on combat alone. This may seem surprising but it actually makes sense. Fighting for fighting sake means either you are playing Street Fighter or it gets boring. Or both. With the rare exception of maybe Deathwatch (which I argue is more a Fight/Talk game) almost all Fighting focused games back the primary game play up with Taking and less frequently Making. Fight/Take is your classic D&D, but it's also RuneQuest, GammaWorld, etc. There is a LOT of great games that follow the Fight/Take model. cWOD Werewolf was a Fight/Talk only because of it's honor system.
Now classic D&D at higher levels shifted the focus from Fight/Take to Fight/Make with kingdom building. Adventure, Conqueror, King knows this and plays it up as a primary selling feature of it's retro clone play. Exalted is a Fight/Make game right out of the gate. It doesn't handle the Fight/Talk aspect as well, even though they tried to shoe horn it in with 2nd Edition. A true Fight/Talk game would require a serious down play on gear and claiming land/items/etc. I know Deathwatch and handful of indy space marine RPGs focus on combat and character interaction over gear fetish and MacGuffin quests, but it's a mixed bag so far.
Those who Talk - Vampire in all it's incarnations is a classic talking game. It's big on politics, dealing with rivals and using power to build up a support base. Any game that focuses primary on diplomacy qualifies. Talking focus games are a lot more common these days with the advent of Monsterhearts, FIASCO, Game of Thrones, and Leverage. I was going to say that Talk/Take is the rarest of the cross builds but suddenly we got Leverage which is a complete Talk/Take game. If I had to put my finger on it I'm pretty sure that Firefly/Serenity based games are this style too. Very much a TV drama genre of games. I guess the Cortex + folks have their niche locked down. Other system like L5R is Talk/Fight, a rarer mix. The focus on honor and Noble combat is where it shines. Pendragon also qualifies.
Those who Take - Welcome to the bread and butter of the mid 80's to early 2000's. These games make of the lion share of what I consider the Golden Era of recent memory. Shadowrun - Take/Talk, RIFTS - Take/Make, Cyberpunk 2020 - Take/Fight, TORG - Take/Make, StarWars WEG - Take/Talk. Mind you a lot of these games focused on claiming land, resources, money, reality, but all featured a heavy focus on skill and cunning. That's the key element of a Take style game. Sure you might be doing something heroic in the long run, but there will be a lot of out thinking foes, being sneaky, and being careful.
Those who Make - This is the trickiest of the 4. Many, MANY, games feature Make as their secondary focus but very few make it the primary. A magical version is the MAGE games of old and new WOD. Technically Demon The Fallen, the cWOD Changeling, and Wraith can fall into the Make territory based on their building up of self and their domain/kingdom building over social mechanics. MAGE works because crafting of magic is key to the setting. Learning, developing, and growing is a personal journey and it doesn't focus on poltics in primary. It's Make/Talk mostly. Non-WOD games could include Reign, Pathfinder's Kingmaker adventure path, late game OSR clones, and I've found Traveller is a big Make/Take kinda game. Big into exploration style missions which fall somewhere between Make and Take events.
There are games out there that try to fill all 4 niches equally with mixed results. Generic games focus on each system individually and sometimes go a decent job of pulling them together. (HERO and GURPS are not so good at TALK but great at the other 3. FATE Core is week in Fight but aces the other 3. Cortex + works well with Talk and Take but fumbles bits of Make and Fight. It also depends on how the group you play with uses the system as built.
What's the point of this then? Well coming down the line I'll talk about the 4 different ficoes and how some systems do it better and what you can steal and reuse elsewhere. And some of my thought about how to enhance an existing game to focus on any one of the 4. My next post will focus on the rare but fun MAKE side of gaming.