Neo sticks are super easy to make. They don't even require actual circuitry other than switches and wire. I built one out of a $5 toolbox from Harbor Freight that is my favorite. The guests can use the SNK one.
The AES stick is very comfortable and will always have a special place in my heart. It was certainly an awesome pack-in controller, but it actually is kinda cheap and sucky compared to something serious. The now common blinged out fighting sticks we see at all the big tournaments make the AES stick look like a NES Advantage. The AES stick feels, sounds, and is thin hollow plastic and it's so easy to accidentally hit the Start button in the heat of gameplay that they actually started writing software to have Select pause the game instead of Start.