The System Shock 1 remaster in particular is excellent. It's not just a graphical improvement, they improved the controls and inventory interface and a host of other legacies from from DOS-era gaming that did not age well.
It's well received after launch, yes. There's been plenty of screeching about "not being true to original" and "this looks ugly" and "this looks wrong" on the way there though. Just like for this.
Especially for the first remake.
This is why I say the screeching right now based on a trailer means nothing. "Fans" always get mightily offended if someone touches their childhood favorites.
You don't have to be a fan of the game to see the trailer and think it looks bad. I'm certainly not a Deus Ex fan. I played it just once, years and years ago. Yet when they showed the trailer during State of Play I was shocked at how bad it was. It's clearly just some texture upscaling and an update to the lighting. The original looks ugly and this remaster manages to look uglier.
An example of a remaster done right was Halo 1 (which is actually quite an old remaster at this point). They threw a new graphics engine on top but also remodeled and retextured everything. That's what I expect out of a proper remaster.
While I enjoyed CE:A, it had issues. The big one was the loss of bump-mapped textures making everything look flat. They only show up when you use a flashlight.
Games people love usually have a large portion of spontaneity behind their success. This is hard to faithfully capture even if that's your intention, and remasters are usually done on a tiny budget for profit by people who often aren't even familiar with the OG game, which doesn't really help.
There are exceptions though, and also there are some remasters that are not faithful but are good on their own.
I don't care for Deus Ex, but looking at the screenshots I struggle to tell which one is the remaster. It's very clear that they messed up the lighting and the overall mood though. I'd be offended as a fan.
As a GMDX user your comment and the Remaster are both irrelevant. The mentioned mod makes the 1st Deus Ex perfect. It enhances places, items, location, graphics... without breaking the original gameplay and mood to please Gen-Zers.