I've been watching and reading literally everything Resident Evil, in production order. (There is so much. Good god, there is so much. It took me a few hours just to compile the list.) I have Thoughts.
The physical continuity between the main games is fantastic. I started all this because RE9 re-stoked my obsession, and since then I've gotten through the first 3 main games (remakes, so I can't speak to the originals). They definitely used the same maps between 2, 3, and 9, and watching those close together shows just how much. 2 and 3 use the same combinations for the safes in the RPD. In 2 you loot a med kit that's still hanging on the wall in 9, interactable but empty. In 3 Carlos creates a lot of the set dressing that Leon passes through in 2. Sherry hides behind and under the same things Chloe does in the orphanage.
The novellizations do Brad Vickars dirty. Okay so in RE1, Alpha team sets down and fans out, gets attacked by zombie dogs, runs, and as they're running they see the helicopter fly away. A few times throughout the game he tries to radio asking if anyone is alive down there, but the radios aren't working and you can't respond. His final message says "If anyone's alive give me a signal, I'm almost out of fuel," so you then have to get outside and set off a flare for him to come get you. This always made total sense to me: The pilot's job is to make sure they have an exit, and he can't fucking do that if he gets killed or the helicopter gets damaged. Circling the area looking for his people until he runs out of fuel is the exact correct thing to do.
But not according to S.D. Perry, author of the novellizations plus some side novels. For the most part I'm really enjoying the novels, but this one thing drives me nuts. In this version Brad is known as a coward, nicknamed Chickenheart Vickars by the team, a good pilot but unreliable in a pinch. He lost the trust of the STARS by leaving them at the mansion. After the events of RE1 he immediately skips town because he knows Umbrella will be coming for them. When he shows back up in Raccoon City for an undisclosed reason (it's because he was there in the game), instead of being there to help Jill get out and sacrifice himself for her to do so, he's a panicky liability until he quickly gets zombified.
I don't like it. I don't like it at all. Taking off was the smart move, and saved all their lives. Skipping town was the smart move, and would have saved his life if the 3rd game hadn't had other ideas for him. (Barry also sent his wife and kids away because he knew that that was the smart move.) This is slander and I will not stand for it.
Other than that, the novels are an interesting read. It's neat getting more of the internal dialogue. Especially when Ada and Leon meet: She's straight-up using him but can't help being impressed by him. Meanwhile he's incredibly earnest in wanting to help her and keeps saving her life and she's just like "Will you stop that?!" Perry totally ships Claire and Leon though. I don't, but I'm intrigued to see how far that'll go in the novels considering the games very intentionally don't show anything definite happening between most characters, as far as I recall.
I don't like the prequels that add zombies before the Spencer mansion. They do it in Resident Evil: The Book, wherein Chris is contacted by an old friend now working for Umbrella, who disappears immediately, and when Chris and Jill go looking for him, zombies show up. They do it in RE0 when Rebecca runs into a bunch of zombie crap on a train right before finding the Spenser mansion. It just doesn't work. The mansion is supposed to be the "Holy fuck, what his happening?!" first moment that leads to everything else. Rebecca is supposed to be the absolute rookie who dropped her damn gun while running straight to the mansion. It's just such a weird, ineffective way of retconning the beginning of that mission and it doesn't work.
The second movie is surprisingly lore-accurate. Like, the movies sort of take from the games but do their own thing, but Apocalypse pulled a lot from the games, including several of the lesser-known side games. We've got Nemesis, Jill, Carlos, Michail (sp?), and the STARS from RE3. We've got the general idea of a reporter and a black comic relief character from Outbreak. We've got the Ashford name; Alice's new mind powers; and her trick of dropping a gun when ordered, then dropping to the ground to catch the gun and fire it from Code: Veronica. Just overall a lot of things that shows that the people who made this movie bothered to pay attention to the source.
Okay I think those are all my big thoughts for now. I've been doing this for about 3-4 weeks now and I just watched Apocalypse and am now reading Zero Hour (the novelization for RE0), which came out in 2004. The franchise launched in 1996. So far nothing's moved more than a few months past Raccoon City, so I'm actually really excited to get to RE4, but I've still got 3 novelizations and a mobile game to get through first. (There were fourteen things put out between 0 and 4, in a span of 3 years.) This will probably be added to as I continue/remember stuff.