In the original, Mario and his friends are flat surfaces with black outlines, to give the impression that they are drawings rather than computer graphics. While that design is still present in the remake, you'll also see a faint hint of a white highlight around the edges of the character model, just like you'd see on real paper cutouts. It's subtle but pervasive and adds to the feeling that these models are truly hand-carved.
Every part of the world has this attention to detail. When you first enter Rogueport, there is a platform in the main square with a noose on it. In the original, the wooden steps are straight and flat and everything is at a right angle. It's fine as a background element, and the flat noose cutout waves in the wind, so the effect works.
In the remake, however, the steps are a bit crooked and janky. The side pieces of the steps look bent, as if a child accidentally pressed too hard on them while sliding the steps. He's standing, but barely. A mild gust of wind can blow the whole place down. It may seem insignificant, but details like this make it easy to get carried away Paper Mario's world.
This is a situation where the improved graphics of a more modern console increased the design choices from the original game. Switching graphics can mean Mario and friends can look more realistic, but in this case it just means they look more handmade a paper craft model of the Mario van Super Mario 64.
The rich detail the remake adds – with more complex models, better lighting and reflection systems, and higher resolution textures – makes the illusion so much more immersive and delightful. In each new setting, it's clear how much effort has gone into recreating every aspect of the game.
Improvements in quality of life
Faithful recreation isn't always the most ideal way to approach a remake, and thankfully Nintendo agrees. This new version of The millennial door comes with a few features not present in the original, but would have been welcome additions.
The most useful of these, in my opinion, is the Partner Ring. In the original game you had to open a menu to switch between different members of your party. It wasn't difficult in itself, but it was annoying. In the remake, you can hold L and tilt the control stick to quickly switch partners. It's a shortcut that doesn't fundamentally change the game, but is a welcome convenience.
Likewise, if you fail a battle, there's a new option. Previously, if you lost a battle, you had to reload from the last time you saved, which could sometimes be annoyingly far away from where you were. If you lose, you'll see a new “Try Again” option in the remake, which will take you back to the most recent part of the map, saving you time enormous amounts of annoying backtracking.