Now, I am intrigued.
Which one was the duplicate Pierre?
Curiously, I actually know the names of each of these PMs. That may be because I like Canada, or because I am an information junkie. I remember thinking back in 1993 how interesting it was that Canada had elected a woman as Prime Minister.
10 for me (only just - born 6 months before Kennedy was killed). Not being an America, the first one I was aware of was Nixon.
Also - 12 Australian Prime Ministers (I’m doing this off the top of my head, but I think it’s right):
Menzies
Holt
McEwen - caretaker PM after Holt disappeared (until the Liberal Party chose a successor), but legitimately sworn in
Gorton
McMahon
Whitlam
Fraser
Hawke
Keating
Howard
Rudd
Gillard
Born during Carter, 1st memories during Reagan.
BTW, how many Canadian/UK/Aussie PMs is that?
I’ve lived through six U.S. Presidents and six Australian Prime Ministers so far:
Carter, Reagan, Bush I, Clinton, Bush II and Obama.
Fraser, Hawke, Keating, Howard, Rudd and Gillard.
I was born in '78 and have no memory of either Carter or Fraser.
ETA: etv78, there’s your answer.
TY Lobot! Now we need the Canuck and Brit answer.
Twelve, starting with Truman.
Duplicate Pierre. Trudeau served two non-consecutive terms as Prime Minister. So, there were 11 in my list, but only really 10, if you know what I mean.
We didn’t actually elect a female Prime Minister; Brian Mulroney resigned and the Progressive Conservatives handed the Prime Ministership to Kim Campbell, who summarily got completely and utterly wiped out in the next election.
ETA: She was Prime Minister for like 4 months.
10; don’t remember Kennedy, don’t really remember LBJ. I kind of remember his funeral, though. The first election I remember is 1972.
14, starting with Hoover.
Do I win?
Eisenhower, JFK, LBJ, Nixon, Ford, Carter, Reagan, Bush Sr, Clinton, Bush Jr, Obama. I remember them all (though I haven’t lived in the USA since 1990).
Eleven for me.
Now, my grandmother, who passed away last November just before her 108th birthday, saw nineteen in her lifetime. She saw the whole list in the OP, with Teddy Roosevelt before Taft. Grandma voted in 22 straight presidential elections, starting in 1928, and the last time was about three weeks before she died.
I surely hope so! 
Eight Canadian PMs: Trudeau, Clark, Trudeau again (two changes of govenment during Carter’s term in office), Turner, Mulroney, Campbell, Chrétien, Martin, and Harper.
Unlike the US, which counts Cleveland twice, we don’t double-count PMs who served two separate terms (or triple-count in the case of Mackenzie King, who served three separate terms)
Eleven for me: Eisenhower, JFK, LBJ, Nixon, Ford, Carter, Reagan, Bush Sr, Clinton, Bush Jr, Obama.
I don’t remember Eisenhower; all I remember of JFK was his funeral; the rest I remember.
I have the same list as Leaffan.
Didn’t even win her own seat, which is very rare for a sitting Prime Minister; last time it happened was with Mackenzie King back in the 1920s.
Which wasn’t even the PM with the shortest term in office, an honour held by PM Turner (June 30, 1984 – September 17, 1984 - less than three months).
Four.
Twelve, although I don’t remember Truman, being only one year old when he left office.
Twelve. I was born mid-way through Truman’s term.
Three: Bill Clinton, Bush the Lesser, and Obama.
Seven for me. Was an infant during the Ford Administration, and while I have other memories of the Carter era, I do not remember Carter as president at all.
I bet we’re the same age. I remember being pissed that they pre-empted Sesame Street every day for about a week!