What's controversial about video game addiction?

Addiction in neuropsychopharmacology is measured by the chemical change in the addict's body that produces the dependence on the addicted substance.

It doesn't make sense wrt things that aren't pharmacologically active substances. Here's a scholarly paper making the point:

Problems with the Concept of Video Game “Addiction”: Some Case Study Examples

If you are doing something all the time to the detriment of your life, it's an addiction.

Not under current clinical diagnostic criteria. If you were looking for a diagnosis you'd need to go to obsessive/compulsive disorders.

Having said that the DSM V does have one behavioural addiction: Gambling. So maybe we'll see others in the future. At the moment though, it's controversial.