With the Emma is a home wrecker mistress label I have seen here on x-books. I don't think it is fair to Emma at all.
I read the first volume of morrison's run again after like 10 years. My own take on the Cyclops/Emma/Jean triangle is simple. Cyclops was already over Jean. I believe after cyclops came back to the x-men, he had an emotional shutdown and with that, him and jean stopped connecting, while I think he still loved jean, he was not deeply in love with her anymore.
Cyclops was over Jean before he started that therapy with Emma. if it was not emma he started an affair with, it would have been somebody else maybe Psylocke or Wanda.
People are blaming Emma for the break down of the jean/scott marriage but if cyclops really and still loved jean, emma would not have been a threat to them.
I know some will say he still chose Jean in the end before her death but to me, it was out of guilt and loyalty than of love. He would have stayed with Jean and wondered daily of all the possibilities he and emma could have had as a couple.
It was good he got with emma even if their relationship started in a despicable way.