From what I remember, while the overall story is the same, the Remake continuity adds a lot of stuff and changes around quite a bit of of others. I don't recall much from the Remakes of 1 and 2, but 4 (aside how much importance is given to the architect of the mansion, and how Lisa trevor was a victim of the Progenitor virus), for example, has Ada be a mercenary instead of a spy of a mysterious organization, operation Javier was changed from a succesful mission with only Leon and Krausser controlling the Veronica Virus in Brazil, to a failure that got Krausser's entire squad annihilated and was covered up, the origin of Las Plagas is a bit different and Los Iluminados date from hundreds of years ago in Saddlers family instead of being a sham Saddler came up to manipulate people in his plans.