The KiKi Joy has latency issues: You can't even PLAY most fighting games!
You can make your own parallel port or USB adapter, the plans are all over.
But the ULTIMATE controller adapter is the N64-to-USB Adaptoid! Latency? IMPOSSIBLE. This thing has an API that allows programmers to access the pad EXACTLY as an N64 would. You could dump/backup Controller Paks, access the GB Transfer Pak, access a Game Boy cartridge IN the GB Transfer Pak for extra features (Extra analog tilt sensor axes from the Kirby Tilt 'n' Tumble cart anyone?), and even use the rumble pak. Did you ever notice that PC joysticks have a square analog axis and consoles have circular ones? Well, for PC games, the driver for any N64/PSX adapter does the necessary conversion, but when playing PSX/N64 games on PC (Ports or emulators!) this data will have to be converted BACK to circular. This doesn't bode well for serious gamers! In N64 emulators you may notice that you can't do Link's "magic-less" spin attack (Twist the stick 360 degrees and press B). But the Adaptoid fixes this! The API eliminates any conversion at all and thanks to plug-in support nearly every emulator supports direct Adaptoid support (Even UltraHLE was patched to support it and Rumble Paks). Because it provides direct access to the controller AND it's I/O port, ALL accessories will work. Rumble Pak, Microphone Pak, GB Transfer Pak, you can even save your EMULATED game progress directly to a real Controller Pak (Memory Card)! No PSX adapter has I/O! No PSX adapter is "conversion-less." No PSX adapter TOUCHES this. In fact, you've got to see the configuration program! It's so flexible, you can even start coding with C++ like commands to get EXACTLY what you want. Check it out first!