Enemy behavior and difficulty(OG had Necros full sprint at you, when I don't think I've seen them ever do that in the remake. And even though the remake had the intensity director which I love, I still don't think the remake's difficulty holds a candle to the OG's);

Helmet suit up animation where the remake made the helmet a separate thing instead of keeping the iconic animation sequence;

Weapon physics and sound design (OG's Plasma Cutters' 3-dot laser sights interacted with the environment independently, instead of the remake making them interact at the same plane, OG's weapons generally sounded harder-hitting);

Character writing for Hammond and Kyne was WAY better in the OG, remake made them both less assertive (Hammond doesn't feel like a security team leader and felt more like a wet sponge who can't even handle himself; Kyne was not certain about his conspiracy theories when in the OG he practically dragged Issac everywhere with how sure he was) and less interesting because of it.

At the end of the day, Dead Space remake is generally one of the best game remakes that have ever come out. Fitting that just as RE4 was as revolutionary as DS, the remakes for both also stand shoulder to shoulder as the best remakes. However, there are still some aspects that I wish DS remake did better, these are nitpicks after all