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)
