I believe in the species honestly, my absolute favorite and I have a big one is Neomoorea irrorata or wallisii. Fragrant, primitive looking out of bloom, and a real eyecatcher in bloom. Not easy to flower though....
Secondly, Rhyncholaelia digbyana. Easy to flower, heavily scented, and just knock out in form.
Then Rossioglossum grande - flowers are huge and last about 2 months.