In high school, my house was the place to be on weekends for multiplayer gaming. After graduation, everybody left town and I lost touch with my regular gaming crew. I'd say that was the end of multiplayer games for me. I work with some people who play games but we mostly have different tastes in games. I work the late shift and they all have things going on in their lives that prevent us from gaming together regularly when we find a game that we all play.
The best I can think of is to find people on the forums. I'm not a very social person but I'm getting a little tired of missing out on co-op/multiplayer so I've started putting members from the site on my friends list. There's a lot of us who are looking for mature players who just want to chill and have fun. We're all here because we have at least 1 common interest to begin with.