It depends on what you want to accomplish.
- Do you only want to enable people to make payments between each other in a general-purpose currency? Then there is no need to create a new coin for it, just use an existing one.
- Do you want to make an in-game currency that can be traded against fiat? Make a new chain based on an existing coin's source code, and give a new name to it. Optionally you can edit the source code of the coin.
Which coin you choose depends on the specifics of your use case of course. Note that everyone will try to convince you to use their coin.