If you enjoyed Starcraft 1, 2 and are looking for something fresh in its universe, these custom campaigns might be of an interest to you. This subreddit https://www.reddit.com/r/StarcraftCampaigns/ has a list of various great custom campaigns by talented creators like Synergy, LordDz, Mindhawk, Zeralan. A lot of time and effort have been put into each one of them.
Feel free to try them out and give feedback. Each post describes one campaign. There’s currently a short description, an author, a trailer (if available), instructions on how to play, a Discord link and playthrough videos (currently mostly by GiantGrantGames and Jayborino).
If you like the campaigns, you can join the creators’ Discords and even support them monetarily.
If you know more campaigns you’d like to include, feel free to ping me (here or partisan_a on Reddit).
Here are some examples of great campaigns:
Wings of Liberty Reversed. Play as a villain and try to stop Jim Raynor.
Heart of the Swarm: Protoss Edition. A race-swapped campaign playing as a protoss in HotS missions.
Legacy of the Void: 3-player Coop. Play the campaign with friends. Each player has unique Spear of Adun abilities.
Kerrigan Covert Ops (NCO as Zerg). A race-swapped campaign playing as Sarah Kerrigan instead of Nova.
The Dark Story. Completely original protoss, zerg and terran campaigns with a great story, new mechanics and unique mission design.
Brood War Alternate. A complete race swap of original StarCraft and Brood War campaigns with new things added.