You are suggesting that single player games are dangerous and unhealthy. This is ridiculous. That's like saying violent video games create real life violence.
If you already have an overly obsessive personality then yes, ANYTHING can potentially be unhealthy. Even food.
I was "addicted" to an MMORPG (Dark Age Of Camelot) for several years, played it very often, sometimes in marathon sessions spanning 6 or 7 hours. And when I wasn't playing it I was on forums dedicated to it or the guild I belonged to.
But I wouldn't say it was an unhealthy level of addiction. I played it for many consecutive hours only when I had the spare time, usually on a Saturday or Sunday when the wife and kids were doing their own thing or the weather was too lousy to go out. I'd take care of chores, meals and hygiene first of course and I still made it a point to exercise 3 to 4 days a week.
I never called in sick to stay home and play. During weekdays I logged off at a decent hour to get to bed. I still spent time with my kids & wife, still played single player games (though not as much), still read books, watched films, played guitar, had my meals away from the PC, etc.
So I enjoyed it immensely and there was some level of addiction there I guess: I sometimes couldn't wait to get home to log on and I would always check player stats/rankings several times a day. But I'm a somewhat normal person so the game didn't TOTALLY consume me, I still had a life aside from the game.
And when the wife wanted some "cuddling" time, I'd excuse myself from my guildies, carry her up to the bedroom and be back in game 3 minutes later. No neglect there
Seriously, it's no more unhealthy than the need to visit RPGWatch daily.