I come from Vancouver, where I am spoiled with sushi selections at very reasonable prices. There is a sushi restaurant/take-out within 2km walk from where ever you are in the city/suburbs. Coming to San Francisco, I was disappointed in the limited sushi places considering San Francisco is 3x more populated than Vancouver. However, for the last four months I've been testing out as many sushi places as I could. Best tasting and freshest around my neighbourhood is a tiny place in Castro called Warakubune Sushi ($$). Another good place is Sushi Time, a hidden gem with very fresh fish,($$) and Osaka Sushi, Japanese owned with bigger maki rolls ($). My friends have recommended BlowFish Sushi in the Mission area but I haven't tried it yet. It's more unconventional type of sushi and more on the pricey side ($$). Good luck!