(FFS: Typed out a lot, then the power went out..)

What can I say to him to make him see my side of things?

First. Tell him in advance what you would like to talk about and when. Preferably after a quiet dinner when you are relaxed, not hungry and in a good state of mind. Don't jump him with this topic. "I want to talk to you about the state of our relationship at x and x. Is that ok?" Try to respect this. Don't talk late at night or when you are in a hurry.

Start by telling him how you feel, and ask him what his point of view is. "Lately I feel that our relationship is no longer a priority in your life. I think this because I cannot see that you are investing any effort. I feel taken for granted and neglected because I feel like you would rather play video games than spend quality time with me. Am I wrong in assuming this?" Note the use of "I-sentences" in order to phrase things strictly from your POV. The difference between "You care more about video games than me" and "I feel like you would rather play video games than spend time with me" is huge. The goal is to not criticize him so he does not feel attacked. If he feels attacked, he will probably become defensive, and he may defend himself with dismissal, counterattack or berating you for something in return. None of which are ideal.

Also practice non-violent communication which include something that I like which to use a voice that inspire empathy in the listener.

Start by you telling how you see things, then ask him how he feels. Don't ask him first.

"I want to have a romantic relationship where we are appreciating and taking care of each other's needs, but I don't feel that I have that right now. "

"What kind of relationship do you want?"

"What do you think about the relationship we have?"

"What do you think about me expressing that I don't appreciate what our relationship have become? I don't want to be "The needy girlfriend", but I do have needs, and I feel that if I don't bring this up now, I will grow resentful and unhappy without giving us a chance to fix things."

Then be more precise.

"I remember when we did X and Y and I was really happy in those moments, especially when you did so and so. How did you feel about that? I want more of those moments:"

End with a summary with some concrete actions:

"I don't care if you don't care for Valentine, but I care if you care for me. I don't care about Valentine either, but I care for you. I need you to show me that you care for me by taking me on a date. I don't care what kind of that it is, as long as you invest effort into making it romantic. If you can do that, then the next date is on me and we can do something you like. ;)"

Try to avoid bringing up any threats or ultimatums. Unless things get really bad and you are seriously considering ending the relationship after trying for a time. They cause a lot of insecurity and will cause the wrong kind of motivations.