@AdamBeGood Einhander was totally a shock on the PS1. It's fun. I never played it "back in the day", so it's brand new to me thanks to emulation. The graphics are slightly dated, but for the time the 2.5D gameplay is impressive.
I'm not that big of a fan of horizontal shmups, but It's so much more enjoyable than something like Last Resort.
@jrb555 My main pc monitor is at 1440p and I use RetroPie on a separate smaller 480p. Love those pixels, part of the charm, but only if its sharp image. Your tv or monitor have to scale up the 720p to its native 1080p and that is where blurryness comes. If you play on a native 720p monitor, the pixels will be sharp.
If someone posts here in good faith about copyright and licensing and is getting FUD responses, I'm probably going to try to address the FUD.
It's my personal goal in 2018 not to post the same thing in the same intellectual property thread more than once even if it seems no one understands what I'm saying (as we all have been tempted to do I'm sure). On the other hand, if a new poster comes around in good faith like this one who hasn't seen those prior conversations, then yes, I am going to point out what has been omitted by other posters including hyperbole like I did above if no one else will.
@mrmarblz The trackball will need an interface board. Some arcade trackballs are sold without that, so be sure you have a solution for it or add on the interface if you have that option. The controller board will accept the wires from the trackball and will connect to the Pi via USB and should appear as a mouse to the Pi. Same with each light gun. If your table is wired with AC power your USB hubs can be powered and plugged into AC inside the table, so you can add as many hubs as you need.
If the Servostik is just a USB device, it gets 5 volts that way. The current draw would be as much as any gamepad plus maybe more while the server is engaged. Why would this be a problem
I would definitely use a powered USB hub for all of these devices, as you don't want the power to come from the Pi's AC/DC adapter. You don't want the Pi to have power issues because of all of the peripherals attached, and powered hub(s) should take care of that.
In order for the removable arcade controls to connect via USB, they will need to be wired internally to some kind of interface. There may be good choices for this, but a cheap option might be to hack four gamepad controllers and just wire your controls to the buttons etc.
This is an ambitious project. Check out my 4 player cocktail system. Mine is a bit simpler, but I had different challenges. My only question for you is: Why, no spinners?
I know, I follow TWiT and that bradcasting network emits in a national US radio, many users do not want to see RetroPie widely known because of the policies of Nintendo for example but being broadcasted nation wide via a radio station and internationaly via internet, the project is widely known