sbflyfan, OMG.
This is a bit of an odd answer, but I thought the progression of the chemistry between Judy Kaye and Michael McGrath in NICE WORK was very well done. I literally cheered when they finally got together.
I thought Bernadette Peters and Ron Raines paired well in FOLLIES.
And, of course, Kelli and Paulo in SOUTH PACIFIC.
https://newplayexchange.org/users/99643/amanda-delalla