Years ago (okay, probably a decade ago) I read an article in Consumer Reports on alkaline batteries. They said that of all the batteries they've tested, all have almost identical performance, with the expensive Energizer/Duracell being best, but only by a tiny bit (as in powering a flashlight for 105 minutes versus 102 minutes for competing brand). This was true for all batteries, including generics, with one exception. The Rayovac batteries were sub-par. Consistently.
Note that this article is over 10 years old, and back then there weren't as many generics (like my favorite Kirkland AA) or these new super duper Alkalines that you see in commercials. Also, Rayovac could have improved their product.