RE4 gets pinned as the thing that changed Resident Evil drastically, the truth is all the classic games sans Code Veronica and REmake all had different gameplay styles and pacing.
RE1 is more about prioritizing item collection, when to pick up something and how long you should be carrying it. Your picking up a ton keys and items constantly. The boss fights were kinda shitty, and combat didn't feel that satisfying. Still a fun game, but its more of puzzle game experiment than anything else. It feels like you're stuck in this location, whereas RE2 feels like a genuine escape attempt.
RE2 is like an action movie with a couple puzzles thrown in. Item collection is a lot less important. There's more convenient drop boxes, and what you do with items is self explanatory. The number of enemies, the feel of combat, how many scenarios where you HAVE to fight, RE2 is a much brisker and awesome game compared to RE1. Less puzzles, more action, better storytelling. Boss fights are also excellent.
RE3 is a hybrid of RE1 and RE2 with Nemesis being a huge addition. You're killing a lot of enemies and running through areas picking up a lot of items. Its completely different than RE1 and RE2 in terms of area design and pacing.
