That is a tough question. Clearly, the 2 leaders, for me, have been Duracell and Energizer, and I usually buy either one, depending on availability or price. Lately I have been purchasing more Duracell batteries, so I would have to go with them as the best.
If I want something to work extra long I use Duracell but if I don't care then I get Panasonic or some kind of cheapy brand like that.
The copper top battery is the best in my opinion. True it costs a little more than the others but then it also lasts 3x as long too.