If you're making a portable you probably need something to watch it on. (Unless you want to guess what's happening in the game, but I wouldn't advise that) Anyway, this forum is your "Hacking a pocket TV/screen" one-stop solution. Share your experiences and knowledge here.
personally i would use 8, two spaced evenly on each side instead of the corners. sand the tips of the LEDs flat and you should get some fairly even lighting and REALLY bright. i have not tested this theory but it seems like it would be more effective that putting them in the corners.