I'm online right now. It starts up with my pc (which is on 75% of the time whether I'm using it or not). Trying to compare it to xbox live numbers is ridiculous at best. I'm certain there are tons of people playing games, way more than consoles, but the best way to find them would be to look at facebook activity.
OK maybe I don't get your point. Are you suggesting a big percentage of users of steam just let it run on the background and never play PC games? If so then I will say: that is a ridiculous assumption at best.
You can also look at the per game online numbers and compare them to consoles if you like. Can't claim those are "idling in game".
PC gaming is doing OK.