EDIT 2: I forgot about the most important thing. The Triforce, so ignore my false info here. 
Technically you can get to Ganon right away in the original, you just need to get bombs to enter level 9. Bombs are purchasable from the start though, in some cave all the way to the right of the starting screen. The Silver Arrows required to beat Ganon himself are inside level 9, though from the top of my head I'm not sure whether or not you need things like the Bracelet or the Candle or whatever inside level 9 to get to either the arrows or Ganon.
Though it goes without saying if you're any ordinary player you will get your ass handed to you if you do that, as level 9 will already hand you your ass even if you're fully stocked.
EDIT: Wait no, I think you have to have the Bow as well, just the Silver Arrows isn't good enough, need something to shoot them with obviously. So you can get to him, but you can't beat Ganon right away from the start... The Bow is in level 1 though.
