Correct me if Im wrong -- but was "Cheers" the first series to be based around a possible (and eventual) romantic relationship??

I think you're right. I looked at the list of sitcoms in the 80s and before and couldn't find anything close. The closest I can think of is Who's The Boss, but that came after Cheers. I Dream of Jeannie had romantic overtones, but it doesn't compare to Cheers.

Good question, and I agree that Cheers has the distinction of being the first true romantic comedy.