Depends which store brand too. Costco stuff (Kirkland) is almost always really good. Safeway has a good store brand too (O Organics and Signature). Kroger's are like, okay (Private Selection). Walmart's (Great Value) are hit or miss. Natural Grocer's stuff is usually good, and Trader Joe's is usually great. Target's Good and Gather seems good though I haven't tried many since I rarely go there for groceries. Uh... so I guess I mean pretty much everything.
I personally think good and gather is really good. They also own a couple other store brands that aren't apparent. I pointed out an ice cream to my girlfriend, she turned it around and sure enough a tiny target logo.