Sam has talked about this subject in several of his podcasts, but I don't think I've ever tried to address it. I may fail miserably, but I'll try.
Sam and I had one of our twice-weekly "date nights" tonight. That means that from about 7pm 'til we go to bed, we do nothing but have fun with each other. The girl amuses herself otherwise, or goes out, and we do whatever we like. Usually, that means we spend some time gaming.
Yes, it is exceptionally geeky that our favorite not-wholly-private pastime is roleplaying. But back when we had three kids in the house and a lot more stress, we found that we had fallen into really bad pattern. There was always some "business" to take care of or discuss, whether it was about the kids or Sam's job or money or the pets or the house, and somehow those mundane things started sucking up all of our energy. Even when we were alone, the kids, especially, were there between us. We were parents and roommates and partners in the business of life, but we weren't having any fun together, and that can kill romance deader than a fossil.
It's very, very difficult to say, "We're not going to talk 'business' during this time," without having something else to fill up that space. We both read books, we both wrote, we saw friends and so on, but I'm not a big movie buff and I don't play computer games (two of his favorite things), and he's not ever likely to pick up a needle, and neither of us really likes to gossip. We don't watch TV to speak of. We agree on politics and religion and the like so much that, well, there's not a lot to discuss. There's only so much time you can spend in bed together. Sam came up with the idea of playing an RPG, one-on-one.
We started playing as a continuation of a game we'd played with a group that had drifted apart after the campaign was over. It was sort of D&D 3.5, in the world Sam has been building since he was a kid. Over time, we found ourselves moving away from ever rolling dice or looking at character sheets. We were creating story together, and dice just seemed irrelevant. After a while, though, the main characters in that world became so powerful that finding any kind of new challenge for them was nearly impossible. You can only threaten the world, realistically, so many times before it becomes old hat, right?
The game we're playing now started as a campaign we played with a couple we were dating, then got used as part of a novel we were writing together. Some of the information was recycled for yet another campaign with a group that just didn't "gel" for long. The story Sam had created was too good for me to walk away from, though, just because the other players were seldom available. So we started playing whether or not anyone else was with us, and it turned into a private campaign.
Over the years, my world has narrowed considerably, because of my health. I've gone from "just suck it up" to taking a lot of ibuprofen to living on narcotics and muscle relaxants just to get through the day. There's never a time without pain, and the best way to not dwell on it is to be completely absorbed in something. Honestly, there aren't that many things in the world that take absolutely all of my concentration. Gaming with Sam is one of them, because he creates such an incredibly detailed, engaging, world, fills it with complex individuals, and then pulls me into plots that seriously challenge me, intellectually and emotionally.
If the only kind of roleplaying you've ever done involved a canned scenario, or hack-n-slash, I'm going to have to ask you to toss everything you think you know about RPGs out the window before imagining gaming with Sam. We are not talking about "X strangers meet in a bar and decide to go off on an adventure." Think instead of stepping in to the richest novel you've ever read, and taking it into a completely different direction based on what you do (or don't do). Think about improvisation with really good musicians or actors, on a night when everybody is on.
I've really only played with Sam, so I'm exceedingly spoiled. I had been exposed to D&D and Traveller as a teen, but hadn't really played before I met him. We played in a campaign with a different DM once, as an experiment, but it died after two sessions or so. Oh! We also played Serenity for the After Serenity podcast. No insult to any other DM/GM, but I've yet to even hear of anybody like Sam. More experienced gamers have told me they consider him "world class," so I feel fairly confident that my opinion of him isn't completely due to my bias.
We've played with just one or two other people, and with groups of 12 or more. I've played in a couple of the "one-off" games he's written for conventions, with very different groups of people each time. There are definitely some things about playing with groups that I miss, and I hope we have a group again soon. I love sitting back to observe another player's "on stage" time, how they interact with whatever Sam throws at them, their unique styles of playing. I adore the feel of a good group of people who are in character, playing off each other, tossing focus back and forth, working as an ensemble. But playing one-on-one does have its unique joys, and I recommend it to any couple who enjoy gaming at all (or, of course, playing together as a triad or quad, for those who are part of those kinds of relationships).
Sam plays all the characters but mine, complete with distinct voices and their own body language. He comes up with the stories, really—or the beginnings of them, and the plot twists. He's always the GM/DM/ST or whatever you want to call it, the real "author," the creative force.
I have no idea how he does it. He surprises me on a regular basis, always in good ways. I consider it a major accomplishment if I ever surprise him with anything I do or say (while staying true to the character, of course). I know that he "reloads" himself creatively, by watching good movies and well-written shows like West Wing, and reading everything from Horatio Hornblower to Penny Arcade. Water is important. Just about every time he takes a shower, he has to leave time afterwards to transcribe whatever his muses sang to him there. And he does this while continuing to write a novel!
All couples have their little in-jokes, code words, and shared anecdotes. We have not just one world, but two overlapping ones, all to ourselves. We don't spend all of our time together in fantasy-land, but we don't ever want for distraction, either, thanks to Sam. The romance in our relationship is still going strong, and it's definitely well-grounded in reality.