Different application folders

Create 4 user accounts, so each user can have their own Documents, Downloads, Desktop, etc. They will all share the same Applications folder and you shouldn't move applications to another folder, as it causes problems with some apps if you do. If you don't want the Applications folder on the Dock to show all apps, simply create a folder in the Documents folder for each user and name it something like "Apps" or "MyApps". Then select the Applications you want to see and create aliases for them. Drag the aliases to the "Apps" folder and then drag that "Apps" folder to the Dock. Use that in place of the Applications folder on the Dock.

 

Some apps can be installed just about anywhere and work properly, but many have to be in the Applications folder. Best advice? Don't worry about it, and if you really just want more convenient access to the ones you use, place them in the Dock or do as GGJ suggested with a folder of aliases.

jW

 

You may already have an Applications folder for only your User name, some apps will ask you if you want to install for one user or all users, if you ever said yes to only one user you will find another Applications folder if you click on the little house under "Places" in Finders sidebar. If there is one there you are all set, if not make a New Folder there and name it Applications, Make sure you name it "Applications" the same as in the sidebar now and it will become an Application folder. You can tell if you did it right if an "A" shows on the folder and not just a blank folder. Now you can "Move" Apps from the old apps folder to the New Apps folder and they will be only available to that User.
With Games I do it a little different because I never know who might want to play them, but I don't want them scattered all over the "Applications" folder. I made a new Folder called Games in the Documents folder then dragged it to Finders sidebar and Moved all the games from Applications to the new Games folder. So far all the games I have work just fine but some for you may not work.

 

You should also look into alternative file launchers, things that work instead of the Dock, since they allow more customization. DragThing, for example.

 

It's been a few years since I set this up for a friend under OS X 10.3.x but if I remember correctly if you set up separate user accounts for each user (non-admin) and then use the Parental Controls (I think that's what it's called) to choose which applications are available to each user then only those applications with access will appear in the Applications folder for that user. If you included yourself in this scenario then the games, etc. wouldn't show up in the Applications folder when you're logged in under the "controlled" account.