Legally, copyright makes sure that nobody can copy somebody else's ideas within a set amount of time. It usually lasts for 70 years in the UK.
Disadvantages
In the game development industry, a disadvantage would be that copyrighting a full video game could need many individual copyrights, which would get very expensive. Things such as animations, sounds, and code require individual copyrights.
People could also steal your idea before you copyright it, and get a copyright on it themselves. This would stop the real author from being able to copyright it.
Advantages
Advantages would be that since the duration of a copyright is so long, you are almost guaranteed to have no one make a profit off your idea. In my 3D environment I could copyright the design and the individual objects to make sure no one can take my assets and use them in their game for a profit.
Ethical
Ethically, a video game needs to have warnings about using the game. For example, if the game contains flashing lights they will need to have an epilepsy warning.
Disadvantages
The disadvantages here would be that the developers could potentially lose customers.
Advantages
The advantages to giving warnings to users would be that they are less likely to get injured. If they do, they can't sue the developers because they were given a warning.