Although Bay Area Japanese noodle connoisseurs have long insisted you need to go to the South Bay for great ramen, the popular comfort food is beginning to develop a legion of followers here in San Francisco. Identified by a rich broth—milky with emulsified fat—and long, springy alkaline noodles, there are textbook bowls of ramen to be found from the Marina to the Outer Sunset. Here's where to go when the craving hits.