I had seen Planet of the Apes and Beneath the Planet of the Apes a few years, but never Escape, Conquest, or Battle, so I bought the Bluray set and watched all of them. I'm going to spoil all of them by the way.
The original Planet of the Apes is probably still the best, although rewatching it I found Charlton Heston's Taylor pretty unlikeable. He's very cynical of humanity at first, having gone into space to "find something better" as he says. But whenever he gets the slightest advantage over his captors he's suddenly all high and mighty about humans. The apes' whole deal with humans is that they're just animals with no souls, no reason, no divine spark. So faced with that it makes sense that a man fall back on hard on that inate belief that humans are special, but it just seems at odds with Taylor's character. Maybe it's just the acting style, that 60s leading man thing. Feels a bit inappropriate given the performance of the ape actors, who are all great. Kim Hunter as Zira and of course Roddy McDowall as Cornelius both act amazingly well through the make up, as does Maurice Evans as Zaius.
Beneath the Planet of the Apes is a weird one. James Franciscus as Brent is a better leading man than Charlton Heston for my money, but the film itself is weaker. Heston didn't want to do the sequel, but was talked into it as a favour to the producer, and only agreed if he was basically a cameo and he got killed off. So it starts exactly where the last film ended, and after 5 minutes Taylor vanishes. Then Brent, another astronaut, appears and the first half of the movie is just a condensed retelling of the first. Brent discovers the ape city, meets Cornelius and Zira, gets captured, escapes, and only then in the second half of the film do things get interesting. They discover a race of mutant psychic humans living in the Forbidden Zone worshipping an atomic bomb. Which is just weird, although it's probably so weird that it's memorable. As far as pop-culture impace goes, the Alpha Omega bomb cult is probably the second most well known thing about the franchise, second the reveal at the end of the first film of course. It also ends with the world being destroyed, which was a ballsy move.
Given that the world was destroyed at the end of Beneath, the sequel had to get creative. So it begins with Zira and Cornelius arriving on Earth in the 1970s, having repaired Taylor's spacecraft and coincidentally left the planet before it was destroyed, and also having somehow traveled back in time to a couple years after Taylor left. All off screen of course. If you can get past that though it's a very enjoyable film. Kim Hunter and Roddy McDowall return as Zira and Cornelius, being the only apes in the film (apart from another who dies very early on). It's the inverse of the original, with the apes going in front of a committee to prove their intelligence and intentions, and the humans are much more accepting than the apes are. It's essentially a very optimistic depiction of humanities first contact with aliens. The apes become celebrities and everyone loves them. But it's revealed that Zira is pregnant, and this is where the film turns. The Presidential Committee decides (the apes having revealed the history/future of Earth to them) that Zira and Cornelius are honest, trustworthy beings who pose no threat, and that they should be allowed to live out their lives in peace on Earth. But they also decide that allowing them to reproduce could pose a threat to humanity's future, so they rule that Zira's pregnancy must be terminated and they both must be sterilised. Which after the fun and hopeful first part of the film comes across and mind-fuckingly evil. It then becomes a chase film as the apes and their newborn baby flee for their lives, briefly finding refuge at a circus before being found and killed. They left their child in the care of the circus though.
Which leads to the fourth film, Conquest of the Planet of the Apes. Set in 1991, apes are now enslaved. A virus wiped out all cats and dogs in the early 80s, so people started keeping apes as pets, and quickly realised they could be trained for perform basic tasks. Institutionalised ape slavery happened unbelievably fast, but you just have to go with it. Caesar, played by Roddy McDowall, is the son of Cornelius and Zira, raised in the circus but now lost among the slave apes. He keeps his intelligence and power of speech hidden, but slowly begins to build a rebellion. Honestly, it's quite a silly film, but still engrossing. It's weird to see so many people dressed as apes in modern settings, especially because Caesar is supposed to be the only evolved, intelligent ape. They say the other apes are getting smarter because they're being trained, but still. All the apes in this film are supposed to be normal apes, but it's all people in costumes. It still works though, and Roddy McDowall anchors the whole film. As it gets to the end and the apes rise up, all the silliness is turned on it's head and the apes get quite scary, which I loved. Most of the battle at the end plays without score, and it gives the apes a sense of determination and force. To top it all off, the main human villain gets a great speech when Caesar asks him why apes were betrayed, why they weren't loved as cats and dogs were. It pushed Caesar over the edge, and then he gets a great speech. I mean a fucking phenomenal speech. Roddy McDowall's performance in Conquest might be favourite performance of the whole franchise, new films included. However, just when you think it's about the end, Caesar keeps talking, and softens his tone, and it ends on a more peaceful note. Which felt really odd, and I wasn't surprised to find out they tacked on an extra few lines about compassion after test audiences reacted poorly to the original violent ending.
And now we come to Battle for the Planet of the Apes. The whole series has played fast and loose with continuity, but this one takes it to a whole new level. Human civilisation has been ruined by nuclear war, and Caesar has founded his own society of apes, although there's some humans living with them too. But every ape can talk now, and they're dressed exactly like they will be dressed 2000 years later in the original film. All this within Caesar's life time. It's mental. The thrust of this one is that the gorillas in the community don't trust any humans, and don't like how Caesar runs things, and try to seize power. Meanwhile a bunch of humans from the irradiated city discover Caesar's camp and attack it. It all leads up to a big fight and confrontation between Caesar and Aldo, the lead gorilla. It seems to imply an entirely new continuity has been born though, since it ends with intelligent apes and humans living peacefully together. Ultimately it's a dissapointing end to the series.