It's debatable... While it won't work on a dsi, the cycloDS is apparently the best, and then there is that supercard ds2i that has built in gba emulation, as well as snes/nes gameplay. But for the majority and for dsi owners, it's the acekard 2.i
I can't really say much because I only used R4 and Acekard2i. But if I have to choose from those two the choice is easy. Acekart2i. Don't know about the other flashcards. But Acekard feels really good and al games I tried work.
