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Between StarCraft 1 and StarCraft 1 BroodWar, 5 units were added.

The new added units are as follows:

Terran:
Medic
Valkyrie

Protoss:
Dark Templar
Dark Archon
Corsair

Zerg:
Lurker
Devourer


In StarCraft 2: Wings of Liberty, only the Dark Templar remained in the multiplayer. However, most of the old units from broodwar were still in the SC2 campaign. In the SC2: WOL campaign, a lot of super units and heros with upgraded health and firepower of old units were added, but some new ones popped up as well:

Terran:
Spectre
Diamondback
Hercules Dropship
Special Ops Dropship

Zerg:
Leviathan


As for StarCraft Broodwar units that did not make it into the SC2: WOL multiplayer, there were many. However many of them do appear in the SC2 campaign or map editor (which are tagged with an asterisk *). If a SC1 unit has a similar SC2 unit replacement, they are denoted in parenthesis.

Terran:
Valkyrie
*Wraith
*Medic
*Vulture
*Firebats
*Goliath
*Science Vessel (Raven)
*Dropship (Medivac or Special Ops/Hercules dropship from SC2 campaign)

Protoss:
*Scout
Dark Archon
Corsair
Reaver
Dragoon (Immortal)
Shuttle (Warp Prism)
Arbiter (Mothership with limitation of building only one)

Zerg:
*Lurker
Defiler
Scourge
Guardian (Broodlord)
Devourer (Corruptor)