I disagree. Star Wars was not inspired by Star Trek. "Lost in Space" could serve as the inspiring science fiction TV series: even though it owes its existence to Star Trek's idea, it doesn't owe its existence to Star Trek being aired.
So, Babylon 5. Invented in 1986, first airs in 1987... you know what, I think that's too soon. The original story still had some big differences, so it needs time to iron out the story problems. So let's say it first airs in 1989, early in the year.
Main characters (names in brackets are former names of characters I don't know they'd still have in 1989):
Commander Jeffrey Sinclair, commanding officer.
Lieutenant Commander Laurel Takashima (or "Laurel Chang"), executive officer.
Lieutenant (I assume) Susan Ivanova, second officer.
Chief Warrant Officer Michael Garibaldi, head of security.
Doctor Benjamin Kyle (or "Chakri Mendak"), Medlab chief of staff.
Lyta Alexander, telepath.
Delenn, Minbari Ambassador
Londo Mollari (or "Londo Collari"), Centauri Ambassador
G'Kar (or "Jackarr"), Narn Ambassador
Kosh (or "Khosh"), Vorlon Ambassador
Lennier, Minbari attache (was he invented yet?)
Vir (or "Virell"), Centauri attache (was he invented yet either?)
Actors who probably couldn't take the parts they had in OTL:
Jerry Doyle (he wasn't an actor yet)
Claudia Christian (I think she'd be too young - only 23 or 24)
Mira Furlan (she was still in Yugoslavia)