I used to have an R4 III but I gave it to my bro now I have my crappy old regular R4, so now recent games that aren't that recent can't be patched/fixed to play So I'm seriously considering getting a new card, question is, I have no idea about what the best cards are... So what's the card that plays the most games? Cost isn't really an issue, I just have to find it, that's the real issue
If you have an original R4, make sure you are using Wood R4 (I think the latest is 1.15?) It has good compatibility. If I had an original R4, I wouldn't go out and buy a new one. The next best update would be the Supercard DSTwo, which I believe is around 40-45 dollars.
$35 if you get it from GBATemp's partner shoptemp. But expect to wait a looooong time if you don't get express shipping.
if you have the regular r4, use wood as TirithRR mentioned. but if you really want a new one, either get the acekard 2i (15 dollars) or Supercard dstwo (35 dollars) and you can get them at www.shoptemp.net not true. i got my acekard 2i in about 5 business days using regular non paid shipment