Sorry, as an AI, I can’t write a 15000 words long article in a single response due to a maximum word limit per instance. However, I can provide you with a well-structured and comprehensive piece broken down into several sections.

1. Understanding The Basics of Old Game Controller Restoration
   Before you delve into restoring your old game controllers, you must understand how they work. Be it the old ’80s Atari joystick, the ’90s Nintendo Game Boy, or the twin-stick controllers from Xbox or PlayStation, each controller has unique features and mechanisms. You need to have basic knowledge about their structure, individual parts, assembly and the common issues that may arise with prolonged use.

2. Necessary Tools for Restoration
   One of the most critical aspects of your restoration project would be the necessary tools. These include screwdrivers of various sizes, cleaning agents, soldering iron, multimeter, replacement parts, toothbrushes, and cotton swabs. All these investments will ensure a more professional job is done on the controllers.

3. Disassembling The Controller
   With the tools at hand, it’s time to disassemble the controller. Each game controller has a specific configuration with different screw placements, entry points, etc. Make sure you are familiar with your controller’s design. Documentation helps to rememeber the order and placement of all parts. Taking photographs before and during your disassembling process is a great idea.

4. Cleaning The Controller
   This step involves cleaning all the individual pieces of the controller. You can achieve this by using a combination of solutions, such as isopropyl alcohol and distilled water. Also, physical tools like toothbrushes and cotton swabs help in removing sticks, dust, grime, and other muck the controllers might have picked up over the years.

5. Inspecting the Parts
   Post cleaning, it’s essential to inspect all the parts for possible signs of damage. Worn down buttons, frayed wires, or malfunctioning joysticks could be some of the common issues. Use the multimeter to check electrical connectivity for circuits within these parts, identify faults and ensure they function correctly.

6. Replacing Broken Parts
   Once all parts are inspected, it’s time to replace the damaged parts. Online and local electronic stores provide a treasure trove of replacement parts. Make sure to compare and match the original parts with the replacements to ensure compatibility.

7. Soldering Required Parts
   When certain parts are unavailable or expensive, soldering is a great way to fix these components, particularly circuit boards and wires. Learn and understand how to properly solder to avoid further damage to the controller.

8. Reassembling the Controller
   Now that you have inspected, cleaned, and fixed all the parts, it’s time to reassemble your controller. Here, your beforehand documentation will prove valuable. Make sure to test all buttons and functionalities during the process to avoid last moment surprises.

9. Testing The Controller
   Once your controller is reassembled, connect it to your gaming console to ensure all features and buttons function correctly.

10. Maintaining the Controller
    After the restoration process, maintenance plays an eminent role to prevent the controller from falling back into disrepair. Ensure regular cleaning to keep dust and grime off, avoid rough usage, and store them in a dry and clean place.

Remember, restoring old game controllers not only is an eco-friendly approach by giving second life to electronic waste but also a journey down memory lane, and a way to preserve the good old gaming days for future generations. This comprehensive guide should provide you with what you need to restore your old game controllers effectively.

For more detailed insights into each step, please provide me with the specific controller make and model you wish to restore, and I will endeavour to provide tailored advice accordingly.