I am, but only for the written stuff, not the movies. The movies were lagging way, way, WAAAY behind the books and short stories, which IMHO were at their best in the 50s and 60s.
I like both the movies and the literature. Yes, the movies were lagging behind, but certainly not as far behind as the lag nowadays (Star Wars was pure 30s Doc Smith style space opera), and there were some very good ones. And 50s SF films often still dealt with ideas, not just mindless action.
Off the top of my head, some of my favorites are:
Them!
It Came From Outer Space (with its twist ending; few films play with our expectations as well as this one).
Tarantula
Creature from the Black Lagoon
The Incredible Shrinking Man (I’m a big fan of Jack Arnold, obviously)
The Time Machine
Invasion of the Body Snatchers (Nice bit of paranoia.)
I loves me some 50s SF movies!
Just a few fond memories:
The Giant Behemoth – The first and best of the Eugene Lourie dinosaur trilogy!
It! The Terror From Beyond Space – The “original” Alien .
The Monster of Piedras Blancas
The Crawling Eye – Forrest Tucker, yeah!!–screenplay by Hammer’s Jimmy Sangster.
Anything by Roger Corman ; yes, even Attack of the Crab Monsters !
Anything with John Agar .
Oh man, too many to list. But a few of my favs:
X (The Man with the X-Ray Eyes)
(Ok, that’s actually early 60s but still in the genre, I think.)
The Thing
The Day the Earth Stood Still
Forbidden Planet
Them!
Invaders from Mars
When Worlds Collide
And many of the ones the other posters have listed. Great stuff!
Another fan of both SF movies and literature of the 50s, here. My favorites have been named. I never had the thrill of watching them first-run, but as a kid and teen in the 70s, I have many fond memories of seeing them on afternoon shows (CREATURE FEATURE being one that played here in Cincy) and late-night re-runs, wherein even the cheesiest giant spider would scare the shit out of me.
Just love stuff like “Forbidden Plnet,” set in the 23rd century, wherein the male leads have sculpted brylcreme-laden hair. 
Sir Rhosis
Had to mention this early sixties classic: “It Came From Hell” or “From Hell it Came” A tree gone beserk killing innocent villagers, the tree has a dagger in it’s trunk which I believe acts as a lightning Rod which transforms him into this diobolical Wood-Being.
If you’re looking for “goog” 1950s science fiction, then some great stuff came out then:
The Day the Earth Stood Still
The Thing
Forbidden Planet
It! The Terror from Beyond Space
Destination Moon
Invasion of the Body Snatchers
It Came from Outer Space
The Creeping Unknown (The Quatermass Xperiment)
Enemy from Space (Quatermass 2) – an unjustly overlooked gem!
The Lost Missile – another overlooked piece of wonder from Jerome Bixby, who gave us It! The Terror from Beyonf Space.
There were a lot of “missed opportunities” – things based on really good works that got screwed up in translation:
This Island Earth
Invasion of the Saucer Men (Really! Based on a pretty good short story!)
The Twonky (Based on a good Henry Kuttner short story, but turned into weird comedy)
Target-Earth
Operation Moonbase
Then there are the monster pix. The Beast from 20,000 Fathoms gets top honors in my book – it has every 1950s monster movie cliche — except that they’d never been done before, so they weren’t cliches yet! It also introduced new special effects techniques that saved money and time without being or looking cheap. Later movies (even by Harryhausen) repeated the formula, then used cheaper production means.
Kronos was by the folks who made Forbidden Planet. The movie is dumb, but the "monster is awesome to look at. Who would’ve thought that a featureless rectangular box could be made so visually interesting? (in black and white, no less!) This one gets super points for production design, even if it is brainless.
The Monolith Monsters – another truly off-the-wall concept that carriesw it far outside the normal run of giant creatures invading cities.