Sure, but good luck easily getting to Golden Gate Park if you're, say, coming from Mission Bay. And if you can afford to live in the hillier parts of town the odds are good you probably have decent (albeit small) neighborhood parks. The problem with SF is that the public schools suck, the streets in a lot of the "urban" parts are rife with squalor, and the city is a lot bigger than it looks when you're trying to get from one side to the other. I mean, if you live in the Outer Sunset you may as well be in a "suburb".... I think SF requires a pretty specific mentality for one to intentionally raise children there [for people of such means to be able to choose to stay or go].
Most of SF west of the Mission is actually pretty good for raising kids - Noe, Twin Peaks, Forest Hills, Sunset, Richmond, and Lake Merced are all pretty family-friendly if you can afford them.
You're right that they're practically suburbs though. Somebody did a transit-scaled map of SF and it actually takes longer to get from the Outer Sunset to downtown than from Mountain View, 50 miles to the south. One of the biggest problems with SF is that the public transportation system sucks, since it's such a patchwork of independent agencies. (Residents of these areas might consider this a feature rather than a bug, though, because it keeps the homeless, poop, drugs, etc. out of their neighborhoods.)
