Disclaimer: Some of these trilogies, when viewed as a whole, are not exactly great collections of three movies. In some cases, two of the movies were enough to carry a less than stellar third movie. The first trilogy is the perfect example. I have seen the first two movies in this trilogy at least 25 times each, yet I have never been able to sit through the third. Yet, the strength of the first two still bring this to the top of the list.
Also, before we get to the list, movies such as Rocky do not make the list because there are more than 3. Yet, some of the movies I include have added more recent (and terrible) versions, yet the original trilogies make the list. It doesn't quite make sense, does it? Yet, it does. You'll see after you read.
1. The Godfather. The first two movies are two of the top 5 to 7 movies of all time. The third is utter crapola. Yet, this is the top of the mountain. Imagine that. I always stop and watch whenever I see these on AMC or any other channel.
2A. Indiana Jones. I'm only considering the movies starring Harrison Ford as Indiana Jones. Not the 186 year old version in the Kingdom of the Crystal Skull, or whatever it's called. I never even saw it. I just assume it was lousy. But the first three movies were classic action adventure movies in the 1980s.
2B. I know I'm cheating with the numbers here, but deal with it. You're not the IRS. Get over yourself. The Terminator and T:2 were so great, they can carry the flop of T:3 and the what I can only assume will suck T:4. T:3 was so bad I watched it with my brother and we forget we had seen it and rented it again and were surprised when it was terrible the second time and then remembered we had seen it a few months earlier but had blocked it out because it was so bad the first time but we forget and rented it again because we forgot how bad it was the first time and then were surprised when it sucked the second time. T:2 may have been the best action movie of all time. May have been.
3. Just the same as Indiana Jones, Die Hard (the first 3) were incredible. Pure action. Bruce Willis at his best. Then, one generation later, another version with the same aging (decrepit?) star. Still, you have to love the first three Die Hard movies. I think the third one was the best. But #1 was great. As was #2. Just a great trilogy, plus a stupid fourth which I am (once again) conveniently leaving out of consideration.
4. Back to the 1980s (and 1990 for #3) for Back to the Future. How many times have you seen these movies? Every time, they're great, aren't they? I knew you'd agree with me.
5. Major League. Again, like the Godfather series, the third installment of Major League can only be categorized as a disaster. However, the first two are great. Well, the first one is great and the second one is pretty good. Still, the first was strong enough to carry a solid movie and a real flop. And, yes, I am aware I compared Major League to the Godfather. Sheen, Snipes, Bernsen, Berenger and Quaid can compare with Pacino, DeNero, Caan, Brando, Duvall, and Vigoda.
6. I suppose at some point I'd have to include Star Wars. I'm going with the first trilogy (in terms of release), which is the second trilogy (in terms of the story). I guess this was more influential for other people than me, but it has to make the list.
7. Sticking with the science fiction genre, the Lord of the Rings collection makes its appearance. These were good movies, even if they were a bit "nerdy." I'll admit it, I have them on DVD. But I feel kinda dorky because of that. I'll live though. (Disclaimer: I think I'm a little crabby because the Rockets got hosed in Portland. All I'm saying is any time Joey Crawford is involved, the home team wins and the series is extended. I'm not saying the NBA is fixed. I'm not saying refs are crooked.)
8. The Man with no Name trilogy. If you don't like these, you're not a good person. Clint Eastwood at his best (and not his leathery-ist).
9. Even though he can't act, Keanu Reeves did star in the Matrix trilogy. Even if this may have been a Biblical allegory, the Matrix was still pretty dang cool. It did start the whole bullet dodging sequence.
10A. I considered making this higher on the list, but the third movie left such a bad taste in my mouth. It really was terrible. But the strength of Captain Jack Sparrow, who was actually in the first two movies (and not so much in #3) allows The Pirates of the Caribbean to round out the list.
10B. The Bourne Series. Look, I know a lot of people loved this movie. But I fell asleep watching one of them. In the theater. During the afternoon. It just didn't deliver the way it could have been. Just like Pirates, this was a lot of hype and marketing and not much in the way of a good movie. Both make the list because of potential, but rank this lowly because of failure to live up to that promise. Disagree if you want to. That's what the comments section is for, folks.
Honorable mention: Rambo, Blade, Alien, El Mariachi (Had it not been for Once Upon a Time In Mexico, this would have made the list) and Naked Gun.
Not so honorable mention: The Fast and the Furious, Crank, The Transporter, Scream and Final Destination.