Im actually stuck at the same step too. Im building a cocktail based on Lindstrom's Pac-Man and plan on only playing the vertical "classics". Not really classics, but definately the Pac-Man series, Galaga, etc... but also including 1944/45/xx games and other vert shooters, and also the good vertical puzzle games. Maybe "Popular Verticals" would be a better term.
Ive been browsing through MAWS and cant find many that have more that 2 buttons, at least ones I want to play. Im afraid though that as soon as I hook up 2 buttons, Ill find a 3 or 4-button game that kicks ass. I am also limited on my width on my panel and real-estate is becoming a premium. Im already having a problem with where to put the Pause and Exit for the player one side. (see attachment)
So I guess what Im asking is: Can you guys think of a good vertical game that I would need more buttons? Before you answer, Im already planning an upright for the SF KOF KI MK Neo-Geo Capcom stuff.
Thx