Star Wars The original Star Wars is one of my favorite films. Empire Strikes Back is nearly up there. Return of the Jedi is a bit disappointing, mostly because the Ewoks irritated me; Tribbles, but not as cute. As for the prequels, not only did I bhate Jar Jar Binks, but, far worse, I was bored by all of the political yak for good chunks of the movie.; so, I never saw the rest of that trilogy.
Indiana Jones Raiders of the Lost Ark I loved. Temple of Doom, for whatever reason, never grabbed me the same way, and I thought it was gratutiously gross to boot; it practically created the PG-13 rating. The Last Crusade I liked almost as much as the first film, because of the humor and the great Harrison Ford-Sean Connery riffs, but also because of that whole theological angle of walking out into nothingness bit. adventure movie. Never saw the Kingdom of the Crystal Skull.
The Matrix I saw the first movie on commercial TV; I was unimpressed, and never saw the others. Probably didn't give it a fair shake. So never saw the others.
Star Trek I've seldom been as bored with a movie as I was with Star Trek: The Motion Picture. I don't know if it was the pacing or what, but these characters, who I liked a lot, were making me restless in my seat. Star Trek II: The Wrath of Khan is the best Star Trek film I've seen, and it was probably helped in the minds of the fans by its improvement over its predecessor. The problem with Star Trek III is that even though big stuff happens, it feels transitional, like the middle part of a trilogy; toss out the first, largely unrelated movie, it really is. As for the others, I saw Star Trek IV with my mother; she was quite confused not having seen III, though she enjoyed it well enough. I liked it considerably more, for which I credit my San Francisco obsession. Star Trek V was awful, just awful. I've not seen a Star Trek movie since, though I would.
Superman The original's iconic, yet I've never seen the sequels, except pieces of III on TV.
Jurassic Park saw the first one well enough, but never cared to see the sequels.
X-Men Never saw the first movie. My wife and I were in a hotel in Maryland on New Years' Eve, coming back to Albany from North Carolina when I flipped on the TV and saw most of X2. It wasn't bad, but seemed terribly busy. My wife, who is not a comic book collector, was totally confused.
Spider-Man I liked the first film quite a bit, though it felt flat occasionally. The second film, though, I loved; possibly my favorite superhero movie, though Iron Man was pretty nifty. Haven't seen the third yet.
The Lord of the Rings It's just not my genre. I tried, and failed, to read the books. I saw the first movie, thought it was fine, but never saw the latter two parts. Yeah, I know: sacrilege.
Mad Max Seems that I'd catch one of these on TV, but never knew at the time which one it was. Probably should actually watch.
Jaws This came out at a time tin my life that I just wasn't going to see movies that might be gory. I have never seen Jaws, let alone its sequels. I will, someday, see the original, at least.
Back to the Future I was very fond of the original. The second movie just felt both dark and like the middle part of a trilogy and doesn't stand on its own. I musty admit that the third movie, with the okld West theme, I thought was a hoot, and I'd end up watching big chunks of it when it used to show up on TNT every other day.
Die Hard Another movie series where I'd catch it on TV but didn't know which episode it was. Looked like fun.
Blade Never saw.
Planet of the Apes I managed to see all five Apes movies in one day. NOT recommended. The original Planet of the Apes is a great film; I totally bought into it. Beneath was a lesser effort, but I actually enjoyed Escape. Conquest was stupid and Battle was an unrelenting bore.
The Godfather This was one of the films (along with Catch-22 and A Clockwork Orange) that got me to swear off gory movies from 1973-1980. No doubt, the original was one of the finest films ever made. But I wasn't going to see II or III.
Rocky Rocky, which I saw with my mother, is a great film; I think it got slapped down because it won the Oscar against showier fare. I rather liked Rocky II, which comes close to equaling the first one. But III to V, awful to more awful. Never saw Rocky Balboa.
The Terminator Yet another series I've only seen on commercial TV, and caught by flicking stations. Seemed that I would like at least the first two films, based on what I've seen.
Rambo Never saw. Never really wanted to see.
Batman Batman, the first one with Michael Keaton, I liked well enough, though sometimes it felt as though Jack (Nicholson) was doing Jack. Batman Begins, though I know I saw it, for some reason didn't stick to the brain; I do recall that it seemed a bit campy, and I never got back into watching Batman movies - though I WOULD have seen Batman Begins (2005) had I been going to the movies. As for Dark Knight...wait until tomorrow.
Alien The first film was excellent. But didn't need to see the sequels.
The Mr. Frog and Jaquandor suggested other trilogies:
Lethal Weapon, Karate Kid Other one I saw only on TV and couldn't tell you which episodes I actually saw. Know I saw the end of KK1, and at least parts of three different LWs.