The Sims 2 - The Sims 2 is usually packaged with The Sims 2 Bodyshop, allowing players to create Sims or Sim Parts. As long as you have an image editor like Adobe Photoshop or Paint.Net, you can create your own CC. It's that easy. The official website at the time also provided Homecrafter Plus and the Content Manager. Homecrafter Plus allows the ability to create new walls, floors and terrains. The Content Manager allows the ability to organize and sort your custom content. If you own SimCity4, then you can use that game to create neighborhood terrains for The Sims 2.
The Sims 3 - Instead of Bodyshop to creating custom content, you can customize your Sims however you want right inside The Sims 3. CAS mode and Buy/Build Mode will have Create-A-Style (aka the color wheel). You can also download Create-A-Pattern and Create-A-World from the official website to create custom patterns and worlds for The Sims 3; just make sure you are logged into The Sims 3 official website, or otherwise you can't download!
The Sims 4 - To my knowledge, there are no official The Sims 4 CC tools.
The Sims 2, 3 and 4 all have the ability to add in custom music files and play them in-game. However, only The Sims 2 allows you to add in your own .avi video files into the Broadcast folders and Games folders, and you can create your own TV shows and Games this way. Not only this, The Sims 2 has great video-processing tools, such as the ability to pause the video-recording while recording the videoclip (just press the 'b' button on your keyboard) and moviemaking cheats. The Sims 3 has the Moviemaker Mode, which allows you to cue animations whenever you want it.
I can't speak much of The Sims 4, because The Sims 4 doesn't come with a manual. EA hasn't released a manual since the middle of The Sims 3 days. If you buy The Sims 4 on disc, you'll just get an empty box with some promotionals and a registration code and directions for you to register on Origin.