hey man, ive been able to make backups of a few games but nsmb was a pain. wasted a bunch of time, discs, different methods. i finally got this to work for me. i finally got to a point where right after i chose the game file and number of players, the screen went to a "disc read" error. burned again because i thought it was a bad burn and got the disc read error much earlier (right after the controller sideways thing). so i tried this youtube tutorial. get the qwiif unpatched version of the game, run the patch he links there (takes a while to process), and install that ios53-64 wad. it worked for me. g'luck. im 4.2u softmod running neogamma r8 b7.
I actually just downloaded a different torrent, unrared it, and burned it with nero. It worked perfectly! The torrent said it was scrubbed and patched already, so that's probably why it worked.