collections like:
games
simulations
animaitions
etc.
I'm actually not sure. I think that you can add your own projects to some of those categories. Other than that, the team looks at recent projects as anyone else does, and will decide "this is a good example of that category."
The Featured collection is a little different; you can't add yourself to that one, for sure. :~) When we come across a project that has a really creative purpose, or has a beautiful graphical result, or has really elegant code, we'll put it in Featured.
is it possible to request projects to be added to the collections?
Sure. No promises.
Games... not my department... I'll ask though.