I met my wife playing Star Wars Galaxies, online. She was member #4 in the guild I ran, The Trade Federation on Flurry, one of a whole crew of people I'd never met in my life. It was a very interesting way to meet, to get to know a person with zero real physical input, no pics (we're too old for that stuff), and we talked on and on about philosophy, life, kids, learning, loving, challenges. For a good while it was just the words, no idea what the other looked like or how old, none of the things you'd normally sort people on before you decide they're worth your time.
The reality is, with no face and no resume in the way, all you've got is the actual person, what they laugh at and how they handle an idea they don't agree with. And in an MMO you see even more, how they solve problems, do quests, handle loot, and deal with moving through the game. That turned out to be the part that actually matters, and it's usually the last thing you learn about someone you met in person, not the first.
At some point we made the leap; she was in Tennessee and I was in California, so meeting in person was a very big deal. I flew out and drove deep into Tennessee, and we met for the first time in a Food City parking lot. It was amazing, we talked for hours.
As they say, "and the rest is history." We married and have been together for 20 years. Meeting her, and a whole crew of people I never met in person but still call friends, is the primary reason I joined the team trying to keep SWG alive [1]. We both still have fond memories of our time together in game, and now in real life.
So when someone tells me online friends aren't real friends, I just smile, because I married mine. And yes, I'm married to a gamer chick, and it's amazing! And all these years later, she's still my friend too. :)