Yeah it's Star Wars for me. Sorry. And Alien, these two are two of my favourites, some of the best, if not the best, in their genres. Other 70s movies off the top of my head I like are The Spy who Loved Me, one of the best Bonds, Rocky, and I guess The Godfather though that one can be a drag.

I know I'm not very original, because these are all like, giant movies, and they are already mentioned multiple times, but hey it is what it is.

Rocky
The Sting
Alien
Network
Star Wars

Comedy - Blazing Saddles (74), Animal House (78)
Drama/Thriller/Sci-fi - Deliverance (72), Jaws (75), Star Wars (77), Alien (79)
Horror - The Exorcist (73), Texas Chainsaw Massacre (74), Dawn of the Dead (78)

I checked my DVD / Blu-ray collection for my favorite 1970s movies:

Science Fiction: Star Wars, Alien, Star Trek, Mad Max, Close Encounters, Soylent Green, BattleStar Galactica, Buck Rogers, THX 1138

Comedy: Life of Brian, Monty Python and the Holy Grail (and the whole Flying Circus show), Murder by Death, Animal House, Smokey and the Bandit, Blazing Saddles, My Name is Nobody

Thriller: Jaws, 3 Days of the Condor, Chinatown, Dirty Harry, Duel, Escape from Alcatraz, The Conversation, The Getaway, The French Connection, The Warriors

Action: Drunken Master, Enter the Dragon, Fist of Fury, Way of the Dragon

Drama: The Godfather 1 + 2, A Clockwork Orange, Death in Venice, Rocky, The Tragedy of Macbeth

Animation: The Rescuers, Robin Hood, Captain Future

favorite trash: Which Way to the Front?, Everything You Always Wanted to Know About Sex But Were Afraid to Ask

Most of my favourites have already been mentioned or will eventually surface (The Godfather, Star Wars, A Clockwork Orange, Rocky, Alien, Taxi Driver, Life of Brian...). So let's bring up the weird one: Bedknobs and Broomsticks. That movie was my childhood! Watched it so many times I broke the VHS xD

I love this movie with all my heart. I still find myself singing the songs from time to time(in spanish, because that's how I watched the movie) 

https://youtu.be/lXuyDW_686k

And that final battle in the end with the revived armors against the nazis... It still blews my mind. No wonder it won an Oscar for Best Visual Effects

https://youtu.be/Z0rRPU_cvGg

By the way, this year it's its 50th anniversary. So... Happy birthday ^^

As a Godzilla fan the 70s were an uneven time for the big guy, but I still really enjoyed Godzilla vs Hedorah, Godzilla vs Mechagodzilla, and The Terror of Mechagodzilla. 

Godzilla vs Gigan and Godzilla vs Megalon by contrast are two of the weaker entries in the franchise.

My mom loved Bedknobs and Broomsticks (in no small part because she loved Angela Lansbury's acting in general; especially in Murder, She Wrote). The movie's basically Mary Poppins again thematically, but with witchcraft and Nazis this time because it's the '70s. Definitely the better concept.

It's been my observation that major wars have often had a sobering, traumatizing effect on society that translates into heightened demand for honest films that are grounded in an often harsh reality. Right after World War I, Americans flocked to dark, serious movies much more than to the more whimsical variety that had often prevailed beforehand. Similarly, the period around and immediately following World War II saw a brief ascent for what became called noir films (as well as your favorite Christmas movie, It's a Wonderful Life; you know, the one about suicide). American movies from the late 1960s and 1970s in general, corresponding to the Vietnam War and stagflation and high crime and all that, also tended to be grittier and more earnest than those popular in the preceding era of peace and prosperity. Similarly, for Japan, the 1940s and '50s were an era of dark and serious movies prevailing following the national trauma of the Second World War and defeat therein. The original Gojira was categorically bound up with that moment in time for the nation.

In contrast though, by the 1960s and '70s, Japan was fully in the throes of the post-war "economic miracle" and the national mood lightened as a result. And so did the general mood of Japanese film-making in tandem. As a result, the 1970s in Japanese film-making were very different (specifically lighter, more kid-friendly, and often more conservative) from the 1970s in American film-making. The transformation of Godzilla from a terrifying symbol of war and nuclear holocaust into a cutesy, silly, heroic children's icon allied to the national military was very much a reflection of those larger social improvements that were taking place. But there were standouts and Godzilla vs. Hedorah and Terror of Mechagodzilla I feel qualify in a sense and on a certain level because of their more issue-driven character and, in the case of the latter, stronger, more involving narrative beats.

The difference really lies in the Jun Fukuda factor. Jun Fukuda was the main force behind the infamous Champion series who really believed that Godzilla should be a simple children's entertainment franchise and nothing more. Terror of Mechagodzilla though saw Ishiro Honda, director of the original Gojira, reprise his directing role for the first time in some time and the difference is felt in many choices, not least of all that of the screenplay, which was written by Yukiko Takayama, making her the first woman to exclusively pen the script for a Godzilla movie. Narratively, the difference is the use of complex characters like Dr. Mafuny and his "daughter" of sorts, Katsura, and their relationship to each other and to the proper heroes and villains of the story. Characters like these lend the picture its distinctive emotional weight and analogies thereto were notably absent from the preceding movie, Godzilla vs. Mechagodzilla, which had been directed by Fukuda. I love those characters! They're way more interesting than the one-dimensional main heroes and villains. Certain scenes near the end of the movie in particular involving them still get me all misty-eyed even today.

Yeah I've long felt Terror of Mechagodzilla gets an unfair amount of stick from the fanbase, I for one consider it one of the best films of the "Showa" (1954-1975) series of the franchise.

Another factor I've read about is that the 70s saw a decline in the Japanese film and cinema industries due to the rise of television, leading to lower budgets which explains why the production values were no longer competitive with Hollywood as they were in the 50s and 60s. They also added blood to the fights to compete with competing kaiju IP like Gamera, as kids love things they perceive to be "grown up".

But yeah, I too enjoyed the darker and deeper qualities of Hedorah and Terror of Mechagodzilla, though I also enjoyed Godzilla vs Mechagodzilla just as good light-hearted fun.

Yeah, the decline in film budgets owing to increasing competition from television was a pretty universal issue for movie-makers everywhere. In this country, it had something of a similar consequence in that movies generally got lower (relative) budgets in the 1970s. But what was going on more largely in society seemed to make a huge difference in the sort of thematic material that film-makers responded to this new challenge with. We had stuff like the Vietnam War going on. Japan was enjoying peace and prosperity, broadly speaking. Those different contexts I think just naturally yield demand for different sorts of content, whether its produced expensively or not.

TV was a huge source of competition for Japanese film-makers though for sure. I mean by the '70s Ultraman was more popular with Japanese kids than Godzilla (and that's NOT exactly because its material was better-written and directed ). Ultraman was sufficiently popular with the kids, in fact, that they even included an Ultraman-alike character (Jet Jaguar) in Godzilla vs. Megalon just to try and bring that audience on board with Godzilla. Ultraman was a TV show. That was really the difference.

Godzilla vs. Mechagodzilla is cute. Those toy towers that get magnetically pulled to Godzilla are adorable! Stuff like that makes me laugh. But the 20 minutes or so of monster content stand out a lot as way more fun to watch than the rest of movie to me. Still, the fight between Godzilla and King Caesar on the one side and Mechagodzilla on the other at the end by itself is worth watching the picture for, IMO, although I'd rather just watch that fight separately from the rest of the movie on YouTube really.