Table of Counters

In case if you only have Original Starcraft, the next best counter provided by Original units preceed the Brood War counter, and the two are separated by an "OR".

Protoss Table of Counters

Unit	Protoss Counter	Terran Counter	Zerg Counter
Probe	Zealot	Marine	Zergling
Zealot	Carrier	Firebat	Zergling
Dragoon	Zealot	Marine	Zergling
High Templar	Zealot OR Dark Templar	Science Vessel	Queen
Dark Templar	Observer + Zealot	Science Vessel + Firebat	Overlord + Mutalisk
Shuttle	Scout	Wraith	Scourge
Reaver	Carrier	Wraith	Mutalisk
Observer	Observer + Scout OR Observer + Corsair	Science Vessel + Wraith OR Science Vessel + Valkyrie	Overlord + Mutalisk
Scout	Dragoon	Goliath	Hydralisk
Corsair	Dragoon	Goliath	Devourer
Carrier	Scout	Wraith	Scourge
Arbiter	Observer + Corsair	Science Vessel + Valkyrie OR Science Vessel + Wraiths	Queen + Mutalisk
Archon	Zealot	Science Vessel + Marine	Queen + Hydralisk
Dark Archon	Zealot	Vulture	Zergling

Terran Table of Counters

Unit	Protoss Counter	Terran Counter	Zerg Counter
SCV	Zealot	Marine	Zergling
Marine	High Templar	Firebat	Hydralisk
Firebat	Reaver	Wraith	Mutalisk
Ghost	Observer + Dragoon	Sensor Sweep + Siege Tank	Overlord + Zergling
Medic	Dark Templar	Firebat	Lurker
Vulture	Dragoon	Siege Tank	Hydralisk
Siege Tank	High Templar/Zealot	Wraith	Queen
Goliath	Zealot	Siege Tank	Zergling
Wraith	Observer + Scout	Sensor Sweep + Valkyrie OR Sensor Sweep + Goliath	Overlord + Scourge
Dropship	Scout	Wraith	Scourge
Battlecruiser	Scout	Goliath	Mutalisk + Scourge OR Devourer + Mutalisk
Science Vessel	Scout	Wraith	Scourge
Valkyrie	Scout	Battlecruiser	Devourer

Zerg Table of Counters

Unit	Protoss Counter	Terran Counter	Zerg Counter
Larva	Reaver	Siege Tank	Guardian
Drone	Zealot	Marine	Zergling
Overlord	Scout	Wraith	Scourge
Zergling	High Templar	Firebat	Mutalisk OR Lurker
Hydralisk	Reaver	Siege Tank	Zergling
Mutalisk	High Templar OR Corsair	Goliath	Hydralisk
Scourge	Dragoon OR Corsair	Marine OR Valkyrie	Hydralisk
Queen	Scout	Wraith	Scourge
Lurker	Observer + Reaver	Science Vessel + Siege Tank	Overlord + Guardian
Defiler	Archon	Science Vessel	Ultralisk
Ultralisk	Zealot	Battlecruiser	Queen
Guardian	Scout	Wraith OR Valkyrie	Scourge
Devourer	Scout	Wraith	Scourge
Broodling	Zealot	Marine	Zergling
Infested Terran	Reaver	Siege Tank	Zergling