It really doesn't mate, why they are mostly FPS's is because thats what most of the developers have wanted to use it for. It's also the game that most of the game market plays besides MMO's but they take a long time to develop, much longer than RTS, FPS. FPS being most often the shortest one. Even though metaphorical that was basicly what you meant. I can tell you this, Unreal Engine is more than enough capable to create a total war style game. Unreal Engine is geared towards FPS for the most part because thats what they primarily develop. Same as 0AD's engine is geared towards RTS Unity -> Casual Torque -> Casual But in the end, its all up to the programmers. about game logic..AI example - Any engine with basic script allowance can have an AI up and running. MMOs NPC's, Mob's etc are all run on the server itself, much of MMO server side is actually not so different from RTS games, but at the same time also very different way of handling them. About rendering - Rendering is not done across the whole map all the time, its turned off when your not looking at it, with the logic and location updates still running, basicly keeping the collision running, turning the renderer off when not on screen objects or using heavy LOD when not on screen, if any rts's had been rendering every units real time constantly it would craw to a crash slope because of all the draw calls it would need even Supreme Commander and Sins of Solar Empire handle it this way. There as called rendering optimalization