I play various games, including WoW, with my girlfriend and it doesn't do any harm at all to our relationship. If anything it is much healthier for a relationship than slouching in front of the TV every evening.
As Billybobser says, if you're in a relationship with someone that's unwilling to share your interests then that's a problem, but not really one specific to gaming.
My wife is not a gamer, although she tried Guild Wars because I play it. We are extremely tolerant and/or supportive of one another's hobbies though, even if we do not share them (hers are crafting-related). If a couple shares core values, and neither has an addiction problem (playing escapist games is just one of many possible addictions), then it shouldn't be an issue.
For a marriage to work common hobbies have to exist and have to be done together as much as possible. If you spend enough time playing video-games that you consider it a decent part of your life than you better be with someone who also shares the hobby and around as much as you. Play those games together and it will be a bonding experience.