That was 10 years earlier. I think I recognized him as the guy from Reading Rainbow but not too much of a household name like other actors at the time.
Yeah, and Reading Rainbow was very popular. It got a bunch of awards and nominations, just as Roots had done. Burton was known for lead roles in two very big TV hits, one of which was ongoing, and he had multiple Emmy nominations. So yes, I'd say he was a household name. He wasn't a mega-celebrity, no, but he was anything but obscure. I remember that the early reporting about TNG mentioned him heavily, because he was certainly the best-known cast member in the US.
I'd imagine that none of those actors were really familiar with general audiences. At least not enough to be draws on their own.
Ummmm... Who cares? None of the TOS cast members were huge names. Shatner was an up-and-coming actor in whom many saw star potential, but he hadn't had a huge hit yet. The rest were working actors who'd been seen in various places but weren't breakout stars. The collective fame of the TNG cast at the start of the series was greater than that of the TOS cast at the start of theirs, largely thanks to Burton.