you could export as png with alpha channel... then import it into a 32-bit game.... and it looks beautiful. Now, about megs... that's another story 
Another solution is to make the background a dark grayish and then color it with your favorite transparent color on photoshop, that way the edges are not as noticeable... like I did in my tutorial: http://netmonkey.cellosoft.com/tutorials/tut1.html
You could also use the magic wand to select the transparency and then go to selection\modify\expand and expand the selction by 1-2 pixels... then erase and you would get pixelated edges without magenta.

Another solution is to make the background a dark grayish and then color it with your favorite transparent color on photoshop, that way the edges are not as noticeable... like I did in my tutorial: http://netmonkey.cellosoft.com/tutorials/tut1.html
You could also use the magic wand to select the transparency and then go to selection\modify\expand and expand the selction by 1-2 pixels... then erase and you would get pixelated edges without magenta.