Please don't say this, either to or about a kids hobbies... Real easy way to turn fun/excitement/pride into shame.
I'm 26 and I seriously can't remember a single time my parents(mostly my mom) cared about my hobbies as a child, unless it was something they could brag about or turn into their own accomplishments. Gaming was constantly met with "The sun is shining why can't you play outside" or "I wish you'd just hang out with some friends instead of sitting inside". When I did something in a game that felt like an achievement, it was met with a shrug from my mom.
People have different goals and interests in life, and that's part of the beauty of it.
Edit: I'm also not really someone that talks about gaming with other people. When my colleagues ask if I did anything fun during the weekend, I haven't, because gaming does not tend to count as either fun, rewarding or fulfilling.