The Distinctive Baritone said: "I'm enjoying reading these, especially since most responses seem to be from people who are old enough to have actually seen some of the greatest performances of the couple of decades (I opened this thread expecting it to be mostly Elphabas and Evan Hansens).
I'll bite:
Denis O'Hare in An Iliad. I've seen many great performances on Broadway and in Chicago, but I saw this one-man show on tour and...wow.
Funny that you mention it, but I felt that I could tell the ages of people based own their choices. For older people, like me, there are some performances that I have seen that I think are historic; three of the four I picked were a thousand years ago...leading one to conclude that I am a close relation to After Eight, who I have come to believe thinks everything past 1970 or so is garbage.
I like too think that is not the case with me, and does not mean that I think that anything remotely recent was not up to snuff. My second choice for female in a play would have been Cate Blanchett for Streetcar, somewhere in the 2010s. I actually chose Dewhurst for what I truly believe was a legendary performance. Similarly, I chose James Earl Jones for a play that was presented about 50 years ago (OMG!!), but I do think that Brian Cranston was incredible 45 years later in the same theatre, if not quite as great as Jones' performance (or Derek Jacobi's in Cyrano, which someone else mentioned).
I admit bias around the women in a musical. I have seen some excellent performances by women in the past 15 years (to set an arbitrary limit on 'recent'
. To me, the only performance in a musical that I would rank even close to Lansbury in (take your choice) or Barbara Harris in The Apple Tree or Carol Channing or Pearl Bailey in Hello, Dolly or Patti Lupone in Evita or Mary Martin in I Do! I Do! or Patricia Routledge in Darling of the Day (32 performances!!!, no less) or Katharine Hepburn in Coco (she deserved the Tony by a mile over Lauren Bacall, who was excellent) or Gwen Verdon in Sweet Charity and Chicago or Chita Rivera in Chicago was, maybe, Patti Lupone in Sweeney Todd or Donna Murphy in Hello Dolly or The King and I; and, as good as they were, I do not feel they were a match for those performances from the 60s -70s - 80s. (Note: I should mention that Alice Ripley's voice was shot (hoarse and flat) when I saw her in NTN; I assume that Tonya Pinkins was also having an off-night for the same reason; and (although I love Bette Midler), I was on the fence with her singing...she just seemed too be giving a lazy performance when I saw her, although the comedy and warmth came through loud and clear; and I somehow missed Christine Ebersole in Grey Gardens).
Re male in a musical, I think Nathan Lane, who I chose in that category, is reasonably near-term, given that the second best (Christopher Plummer in Cyrano) was probably 40 years ago at this point. I also feel strongly that, more recently, Ben Platt and Hugh Jackman gave top 5 male in a musical performances in a lifetime of theatergoing. Add Richard Kiley for Man of LaMancha, and you have it.
I guess the point is that young people are picking performances based on anywhere from a very limited number of years viewing to 10 or 15 years, while old farts like me are picking from decades more (in my case, I have been seeing shows regularly since 1964, along with a (very) few that my parents took me to see before I was even 10 or 11. Our advantage is that we have seen performances they can only dream of having seen; and, actuarially, they get to see a lot more future legendary shows than we will; and as they do, their 'choices' are going to change as they have more performances under their belts.