Curiously, I have just been running over my movie lists, and have updated them a bit. (I am constrained by the fact that I don't watch movies very much at all, not have I ever).
Note: slightly further updated 14 July 2013 (added some Bergman & Fellini films).
Both of the films you mention are on my updated lists, though we should note that calling La Jetée a "movie" is stretching a bit, as it is only 28 minutes long.
My current lists are divided into four categories; all categories mean the equivalent of a book worth at least one star--the divisions are into degrees of proability, because for many I have to go solely by reputation and various critical write-ups. That said, my current list (alphabetical within divisions, ignoring The/A/An) is:
The Adventures of Baron Munchhausen
Alice in Wonderland [1966 Jonathan Miller BBC]
Beauty and the Beast [Cocteau]
The Big Empty
Carnival of Souls [original]
Flash Gordon [modern remake]
The Last Starfighter
The Man in the White Suit
Monty Python and the Holy Grail
The Nightmare Before Christmas
The Quiet Earth
The Seventh Seal
The Temptations of Doctor Antonio [Le tentazioni del dottor Antonio; segment 2 of Boccaccio '70]
The Troublesome Man
The Devil's Eye
The Exterminating Angel (El ángel exterminador)
Faraway, So Close! (In weiter Ferne, so nah!) [sequel to Wings of Desire]
Faust (Faust – Eine deutsche Volkssage) 
The Fisher King [is this really fantasy?]
Hour of the Wolf
The Illusionist 
The Last Unicorn
The Magician [Bergman - categorization questionable]
The Man Who Fell to Earth
Solaris (1972 Tarkovsky)
Solaris (2002 Soderbergh)
The Virgin Spring [Bergman - categorization marginal]
Wings of Desire (Der Himmel über Berlin)
X: The Man with the X-Ray Eyes
The 10th Victim
The Adventures of Buckaroo Banzai Across the Eighth Dimension
A Clockwork Orange
Brother from Another Planet
The City of Lost Children
Harvey [DuPont Show of the Month: Season 2, Episode 1, 22 Sep. 1958] *
The Rocky Horror Picture Show
The Truman Show
Not at all sure:
The Cabinet of Dr. Caligari (Das Cabinet des Dr. Caligari) 
Nosferatu (Eine Symphonie des Grauens)
* Note that the Art Carney "Harvey" is available on DVD, but only as an off-the-air recording (though said to be of passable quality).
By no means are even the ones I have listed as "definite' (meaning I've seen them and think so) of equal quality: some are one-star and some are five-star, but I don't feel like getting into such nice differentiations on such short lists. Also, some of these are serious films and some are comedic, which I do not think lessens their merit.
I'd be interested in some opinons on whether "8½" or "The Fisher King" really qualify as "speculative-fiction" films (or on any other films of merit that one might not think of as specfic but that could qualify). Some of the old masters' work (Bergman, Fellini, and that lot) might fit; I need to look over their lists of works.
Eric Walker, webmaster