I'm going to tread lightly so here goes...
You are already too far ahead of yourself.
First decide what kind of cab you want to build. Cocktail or Upright? Horizontal or Vertical? 1 player, 2 player, or 4 player? etc.
I'd start with these questions first and that helps you narrow it down real quick. Then decide what kind of ARCADE games you want to play on the cab. Unless there are some NES games you want, you'll probalby find that console games should remain on consoles themselves.
In other words...my rule of thumb is decide what kind of cab you want and make a list of "must have games" (I bet it is less than 25 or so) and then build your cab around that.