A common complaint about the films is that they deviate too much from the source material, but is that really the case? In truth, I think the films are heavily based on the source material, especially G1. Sure, there are individual characters that are different from previous incarnations. Crosshairs is little like previous incarnations. There's no indication Sideways is anything like the UT ally of Unicron. However, as a whole they are heavily inspired by previous incarnations. Let us count some of the ways the films are like the source material, especially G1, and this will include what is known about The Last Knight so far. These are not always in order of importance, nor is the list exhaustive, but it shows the many similarities to the source material the films have. 1. The Transformers are alien robots that transform into vehicles, objects, and mechanical animals. 2. The Transformers are life as we don't know it. Cybertronians are machines that think and feel and in many instances use language. 3. The Autobots and Decepticons are rival factions in a civil war. Autobots are generally more willing to defend humans and other life forms, but the Decepticons are perfectly willing to find human allies if it helps them attain their goals. 4. Bumblebee as a kid-appeal character befriending a Witwicky. 5. Optimus Prime is the current leader of the Autobots. He is a leader in a war that is more violent than depicted in the cartoon, but he still has the core of the original character. Like his original counterpart he has to fight Decepticons and other enemies, but he never seems to enjoy killing, and he thinks "Freedom is the right of every sentient being." 6. Megatron is the current leader of the Decepticons who considers Prime his rival. He thinks little of humans and will happily destroy Earth if it means getting his way. His TLK bio even has his original motto: "Peace through Tyranny." he doesn't trust or like his second-in-command much. 7. Earlier films more closely resemble the first two seasons of the G1 cartoon, while more recent films appear to have a post-movie science fiction feel. The progression is very G1. 8. The Transformers were made by the Quintessons (now that Lorenzo di Boneaventura confirmed it) to be a race of slaves. Only later do they become free beings. The Transformers were built, and their creators want them back! 9. The Dinobots are a team of brutish Autobots that transform into metallic dinosaurs. There are instances where they clash with their fellow Autobots. 10. Jetfire is a Decepticon who transforms into a jet and chooses to join the Autobots. Sunbow Jetfire appears to sacrifice his life, and ROTF Jetfire actually sacrifices his life. 11. Revenge of the Fallen has aspects of Changing Gears. 12. Dark of the Moon has plot points from The Ultimate Doom and Megatron's Master Plan. 13. Age of Extinction, like Five Faces of Darkness Part I, has alien bounty hunters hunting the Autobots to take back to the Quintessons. Additionally, AOE also has aspects of Animated with Megatron manipulating the humans and what not. 14. The Last Knight appears to have Prime getting corrupted and/or controlled as in Dark Awakening. The confirmation of Quintessons further suggest it. 15. Also, TLK has Transformers in medieval times much like "A Decepticon Raider in King Arthur's Court" and "Man of Iron." 16. Starscream is the second-in-command of the Decepticons, transforms into a jet, and has banter with Megatron in ROTF and DOTM. 17. Soundwave is loyal to Megatron and specializes in espionage and communications. 18. Wheelie humping Mikaela's leg is not the first time a Wheelie has fallen in love with a human. Headmasters Wheelie sure likes Papika. (Okay, this may be a stretch, but it's a fun observation nonetheless.) 19. Pretenders 20. It has been confirmed Cogman is a Headmaster Transformer in which the head becomes a smaller robot. 21. Laserbeak and Ravage are minions of Soundwave's. 22. Ravage is mechanical feline who sneaks around on reconnaissance missions. 23. Laserbeak is creepy and is a mechanical avian-like creature. 24. Devastator is made up of the Constructicons. 25. Mixmaster transforms into a cement mixer. 26. Brawl transforms into a tank and is a total brute. 27. Lockdown enjoys being a bounty hunter who enjoys his hunts, is loyal to neither the Decepticons nor Autobots, has a ship, and has a hand that turns into a hook. 28. Lockdown killing Ratchet is arguably a tribute to their Animated rivalry. 29. Ratchet is an Autobot medic. He is also an on screen death in a time period when many Autobots were getting killed just like Ratchet was an on screen death during the 1986 film when many Autobots got killed. 30. Ironhide is a gung-ho Autobot who loves to insult and fight Decepticons. 31.Drift is very much like his IDW namesake in many ways. 32. While not one of Soundwave's minions in the film, Frenzy is a Decepticon minion nonetheless. 33. Cade Yaeger is very much like Sparkplug in that he can repair the Autobots, and now in The Last Knight reports indicate he is considered a friend to all Autobots and going around repairing Autobots thought to be dead. 34. Humans attempting to build their own Transformers. Especially humans basing one of their own Transformers on Optimus Prime. 35. Shockwave being a one-eyed Decpeticon who isn't especially talkative, has a cannon on his arm, and even doesn't have the best aim in some instances. 36. Multi-headed, dragon-like Transformers being present. 37. Grimlock is a fire-breathing Tyrannosaurus rex that is stubborn and is the apparent leader of the Dinobots. Also, his Last Knight description sounds very much like some previous cartoon versions of the character. 38. Slug resembles a Triceratops. 39. Bumblebee facing (and possibly Hot Rod given his presence in the movie) a controlled Optimus Prime. 40. Hound may not resemble his G1 self in a number of ways, but he is still a green Autobot who inside has a heart of gold. 41. The Decepticons use drones in their ranks just as in many scenes on Cybertron in Sunbow. 42. Hot Rod's description sounds like his G1 self in some ways. He is brash and slightly arrogant, and he does have a cool car mode. 43. Que/Wheeljack is an inventor whose inventions some times don't work, like when the Boomstick doesn't work when Bee is apparently going to get executed. 44. Space bridges are a thing. 45. While in earlier films we see the meteor modes of Earth-bound Transformers, later movies show Transformers using spacecraft as in most series. 46. Dinosaurs are connected with Transformers in many series, from the Savage Land to Dinobot Island to the Quintessons causing the dinosaurs' extinction in Age of Extinction. 47. Cybertron is a relatively barren place in Movie times just like there were few Transformers remaining on Cybertron during the first two seasons of the cartoon. 48. Sqweeks has a strange speech pattern just like many other Transformers do, especially kid appeal characters. Wreck-Gar, Wheelie, Shrapnel, Grimlock, and now Sqweeks all have funny ways of talking. 49. The Transformers are given life my mysterious mcguffins in both the movies and other continuities. 50. Optimus Prime has the Matrix of Leadership.
Everyone refers to G1 as the source material. But really, the films draw a lot from different TF shows/comics. No one's really saying the films are unfaithful, they just want better stuff I think.
But the thing is there are people who make arguments from the point of view that the films are not faithful enough, when in reality none of the big budget film franchises are more faithful to the source material. The Jurassic Park films? Nothing like the books beyond the original movie, and even the original film lacks some of the ideas and details in the book. The Hobbit films are way different from the books and bloated beyond belief. The current DC and Marvel films are not any more true to the source material either. If anything they are even less so. If people are going to dislike the Transformers films for their execution then that is perfectly fine, but at the same time it seems to me a lot of the hatred (not criticism, but hatred) really stems from the films not matching the inner visions of fans.
That's one of the problems. They Base it on the G1 cartoon which was mostly awful. They seem inspired to ignore the good parts of the franchise.
The old G1 animated canon is actually ripe to be plundered for ideas that 80's writing either ignored or did bugger all with.
I think it's safer to say that the movies are more based on Transformers in general and less based on G1 specifically.
Just a minor nitpick but source materials might be a better term than source material. The movies seem to be taking things from all over the Transformers mythology and even though Hasbro has tried crazy ideas of hey we can make it all fit together we still have different mythologies out there between all the comic book and cartoon series. Primus help us they might even draw from Kiss Players before it's all over.