Multiplayer shoot em up games for PC/Windows with 4-player support

Netherspace 2

Players: 4 local, 0 online

Airstrife: Assault of the Aviators

Players: 4 local, 0 online

Jamestown

Players: 4 local, 0 online

Mercenary Kings

Players: 4 local, 4 online

Chicken Invaders: Ultimate Omelette

Players: 0 local, 4 online

Zytron II

Players: 4 local, 0 online

1993 Space Machine

Players: 4 local, 0 online

Aces of the Luftwaffe - Squadron

Players: 4 local, 0 online

Shoot Many Robots

Players: 0 local, 4 online

Aether Drift

Players: 4 local, 0 online

Retrobooster

Players: 4 local, 0 online

XenoRaptor

Players: 4 local, 8 online

Friendship Club

Players: 4 local, 0 online

Spareware

Players: 4 local, 0 online

Rogue Continuum

Players: 4 local, 4 online

Shutshimi

Players: 4 local, 0 online

Zombie Party

Players: 4 local, 4 online

Dariusburst: Chronicle Saviours

Players: 4 local, 0 online

Stardust Galaxy Warriors: Stellar Climax

Players: 4 local, 0 online

Overdriven Reloaded

Players: 4 local, 0 online

Xenoraid

Players: 4 local, 0 online

Riders 2491

Players: 4 local, 0 online

Toon Shooters 2: The Freelancers

Players: 0 local, 5 online

RiftStar Raiders

Players: 0 local, 4 online

Jamestown+

Players: 4 local, 0 online