I have a 2 year old daughter with a second on the way, and both my husband and I still find time to run. It's not selfish and it stops us both going insane.
The key seems to be organisation. Rather than running together as we used to do we have a rota (boring but it works). I have Tuesday nights and Thursday nights to go running, while the husband has Monday nights and Wednesday nights to run. One of us has a lie in on Saturday mornings, the other on Sunday mornings. And when the one who's had the lie in gets up, the other goes, gets changed and goes out for a run while the other does childminding and eating their own breakfast.
That hour and a half run on Sunday morning (well, it used to be that far, I can't quite manage that these days) set me up for the rest of the day - and you can deal with anything if you're mentally well, even sleepless nights.
I've just read The Penguin's page on the Dec 2006 issue of Runners World and the comments about running apply to parenthood. The longest runs (and sleepless nights) end and even the worst runs (and tantrums) are over eventually. Unfortunately so are the great runs and those magical moments. Good or bad, long or short, at some point they all end, and as a runner and a parent all you can do, is do it again.