wolfsite: This can be tricky to answer as it all depends on which game you are talking about. Some older games could have controller support but limited to controllers of the time but may also require drivers that are not available on modern systems and would need some work. An example would be classic games that used a gravis pad or earlier style of controller that used an older connector like a 15 pin or similar.

Many instances a 3rd party program that can map keyboard to joystick can also work but would need to be manually set for each game.

Some front-ends can also emulate these features as well but I don't know much about this field.

So again it all depends on the game.

malidicus: I was afraid of something like that.
I use RetroBat mostly and it auto maps controllers and of course you can customize the binds if you want.

malidicus: I saw that about Mortal Kombat 1,2,3. One of the main reasons I asked is because Fallout 4 supports controllers but the free Fallout London (which requires having Fallout 4 already) does not specify controller support. I thought that was so odd.