hello everyone. Without wishing to soapbox, i have enough skills to bring a project mostly to completeion and will learn the rest as i go.

I've esperimented with writing my own 2D engine in flash/as3, but it started to feel too much like reinventing the wheel and i dropped the idea for now. Engine licensing seems a far more efffective means to go.

I'm interested in knowing about the main engines in existence, and their reasons for being. Were engines designed with an optimisation/focus on a specific genre ?

could i make a 4x strategy game in cryengine if i wanted for example? I've never seen it used for anything besides FPS games. Is there an engine which is more focused on pathfinding and AI, for example (those being critical aspects to that genre)

And also a more general, idealogical question. Is it wrong to entertain the idea of using a different/most pappropriate engine for each project, or does it make more sense to find one consistent engine and use it as the basis for all of my output ?

Some engines have genres in mind, some don't. I think Cryengine can be used for anything, but maybe since it started as the Crysis engine (I don't know of previous released games using it) almost everyone use it for an FPS. The same with UDK. Some engines for PointAndClick adventures exists, and I guess it's not easy to use them for another type of games. As a curious example of uncommon genres within an engine, here's a tetris clone created with the Warcraft 3 engine:

I don't know any engine focused on AI. Unity for example has a tool for pathfinding, but it's not "focused" on AI.

For the last question, it can be one or the other depending on lots of things. If you have a company you probably want one engine, you don't want to spend time learning new engines every time you start a project or hiring experienced developers every time you change the engine. But, if you find an engine that will make development easier and the cost of learning is less than developing it in the know engine you might want to change. If you're learning maybe it's good to try more than one, but it will also mean you spend time learning the new engine instead of making the new game.

Have a look at the engine DB on devmaster.net

Also, all of the big engines nowadays are pretty much multipurpose... yes, you can make a strategy title in Cryengine. You might not be able to use all the FPS-oriented helper classes or tutorials, you might need to work around some other limitations, but its a good start.

Generally I would recommend starting out with Unity or Unreal Engine 4 for 3D Engines. They are the big commercial engines out there in the Indie-space, both have free or low-cost licenses available, both have huge communities and a large set of available tutorials and APIs, both are pretty much up-to-date (UE4 certainly is cutting edge, Unity will be again with the Version 5 coming out soon) .

About using different engines for each project: AFAIK most studios nowadays stay with their chosen engine for as long as it makes sense. Relearning the engine API and Editor takes time, you might need to redevelop needed plugins and editor tools you already have for the old engine, you might need to rebuy licenses for middleware solutions, and so on.

As said, most engines nowadays are pretty much multipurpose, and there is almost no engine out there that really allows you to develop withour writing all the game logic on your own (there might be tutorials, template projects or helper classes that provide you with part of the functionality, but none of this really is part of the core engine), so there is little functionality that one engine can boast another does not provide (For example, Esenthel Engine has built in Parallax Terrain shaders and Terrain Streaming, ideal for large openworld Games. You can do the same with thirdparty assest you can get for unity, its just not built into the core of the engine).

As an example:

WoW was built with the engine from Warcraft 3... of course, heavely modified (and back then there were no cheap options for engine licensing, so investing lots of money into making an aging RTS Engine work as Third Person cam MMORPG engine made still sense).

Today, this will be pretty common (All the World-of-... Games from Wargaming will be using the same aging Bigworld Engine WG licensed for World of Tanks. WG even bought Bigworld later on, and re-engineered the whole engine when most people were pretty much sure the engine itself was old and dated, and the only good part really was the netcode. They did not not dump the engine, even though there might be better engines out there nowadays for little money, they choose the old patched up Bigworld engine even for their newest game World of Warships. Shows how much of an effort they expect porting to a new engine would be).

Most mainstream 3D engines were built with shooters in mind, but that doesn't mean they can't be used for other genres. the scrapped remake of CnC Generals used Frostbite, and Source was used for DoTA 2, a MOBA. I've never used CryEngine, but I think you can, if you wanted to, make a 4X game on it.