2 - 3 controllers per system on average as long as the systems are popular. When the systems become legacy, I often sell one or two controllers since my friends prefer multiplayer on the newer systems.
2 Competition Pro for C64 and Amiga
3 PS1 controllers: 1 digital, 1 analog + 1 DualShock 1
1 GameCube controller... sold the second controller
2 Xbox "Controller S" gamepads
1 Wii Remote+ and 1 Nunchuk (connected to my Wii U)... sold the second set together with the Wii
3 Xbox360 controllers: 2 wired (perfect for PC, SteamLink + Android devices) + 1 wireless... sold the second wireless
2 PS3 controllers: 1 Six-Axis + 1 DS3
2 Move controllers (now used for PSVR) and 1 Move navigation controller
1 Wii U tablet controller... sold the Wii U Pro controller
2 Xbox One controllers: 1 standard + 1 "Ocean Shadow"
4 PS4 controllers: 2 DS4 (can also be used with my Xperia phone) + 2 Vitas (remote play)
1 Aim-Controller for PSVR
1 guitar controller + 1 drum for Rock Band / Guitar Hero...
I also have some older pc controllers for the gameport laying around: the "Gravis PC Gamepad" (SNES-pad shaped) and the "Gravis Gamepad Pro" (PS1-pad shaped) were perfect for any PC game with digital controls; the "Gravis Analog" and "Gravis Analog Pro" were great for games like Wing Commander and racing games.
