Starman
Adventurer
One question, when you say games, are you talking about RPGs with friends or are you also talking about video games, MMOs, etc?
Because I think that RPGs are a social experience, an outlet for creative energy and personal growth that can really benefit a person. Video games, on the other hand, are IMO time wasters. If we're talking about video games here I agree with your girlfriend, they should not be a significant part of an adult's life. There is no compelling reason for an adult with responsibilities to set aside 50 hours to play the newest God of War or whatever, and it makes you seem selfish for spending so much time with them.
But you are also just 21. I may have thought I was going to play video games my whole life when I was 21. Now I have hundreds of the things gathering dust.
If we're just talking about getting together with friends for a hobby game, then I would say reflect on what playing D&D means to you and tell her why it's a part of your life.
That's just ridiculous. A person can be an avid video gamer and still live a balanced life as an adult. Video games can also be a very social activity whether gathering for multiplayer games or playing MMOs. The idea that video games are only for kids is ludicrous.