To start with, it's a remake. Not all remakes are bad, just the vast majority. This was a remake of a fairly recent (1980) film that was pretty decent the first time around. Strike 2. It was also a remake that toned down sex and violence to make an R rated premise fit a PG-13 rating.
The Fog isn't just any PG-13 remake of a 1980 film, though, it's THE PG-13 remake of a 1980 film. It manages to combine all the things that reasonable people hate about Hollywood into 100 minutes of snoozetime. It's got a decent budget, which it spends on reasonably good special effects and competent craftsmen for all the sets, costumes, locations etc... The things that Indie filmmakers have to scramble and horse-trade for. It's got a couple of C-list leads including Maggie Grace, who's decent for the first half of the film and then appears to lose all interest about the same time the audience does, and Tom Welling who is literally wooden enough to be mistaken for a prop. I sometimes forgot he was even in a scene since all he does is stand around looking kind of handsome and speaking his lines from time to time (Most of them being "We've got to get out of here" in response to having watched someone get butchered by the ghostly baddies. Thanks Tom, that's really good advice. Don't wait around to be butchered. I'll have to write that down.)
It's also got a writer and director who don't give a fuck about making a decent movie.
And why should they? The producers don't seem to care either. According to most of the reviews of the film promotional materials claim that the Fog attack occurs exactly 100 years after the founders of the town betrayed the lepers. The movie shows that this is categorically false, since the betrayal occurs specifically in 1871 and the movie is clearly set in the late 90s or 2000s (There's a guy with a laptop/webcam, and another guy with a digital camcorder.)
That's just one of the many stupidities the film inflicts upon its audience. In addition it suffers from "No Rule Syndrome," which is when a horror movie defines neither the rules that limit what the baddies can do/who they kill NOR the rules about how to stop them, "Random Prejudice Syndrome" The film's villains are a group of lepers who in life were peacefully trying to negotiate the purchase of some land to build a colony and were murdered. They come back 130 years later to kill the descendants of those who betrayed them and anyone else who happens to live in the town built on their land, BECAUSE THAT'S HOW LEPERS ROLL. They just fucking kill people from beyond the grave to satisfy their thirst for revenge. The movie implies that the Lepers are going after the families of those who made the deal, but they seem happy to murder a black guy whose parents moved there from Chicago. There are a bunch of other syndromes too like "Little Kid In Trouble" and "Characters who disappear and reappear for no reason" but frankly the worst aspect of the film is its failure of imagination.
For one thing it takes about an hour before the shit really hits the fan. This is fine in a film like Jaws where the characters and setting are interesting enough that the movie would be worth watching even without the shark, but The Fog exists purely to show people getting killed by ghostly lepers. Spending an hour fucking around with small town politics is pointless. Just tell us who the characters are, roll the fog in, and start spilling blood. The film also steals liberally from other iconic images. The ship the lepers sailed on is an old sailing vessel that could come from 1600 as easily as 1871. Why not make things interesting. When's the last time a movie showed a ghostly steam vessel? That, at least, would be an original image. Then there are the old horror standby shots. "Oh look, the old woman is looking into the sink, very very slowly. Meanwhile we are seeing a sink's eye view of her, as if there's something lurking in the drain and it's looking up at her. I WONDER WHAT IS GOING TO HAPPEN HERE." And just randomly stupid things like the fact that the fog ghosts go after everybody, or the stupid drunk preacher or...whatever.
The thing is, this COULD have been an interesting movie. In fact it was, the first time around. It could have been about something. It's not an unworkable premise. Instead what we get is decent craftsmen working to service a bad script and bad director all to create something that can be sold via a marketing campaign. All they cared about was creating a few money shots of people being killed, and then enough coherence that the audience wouldn't demand its money back. That's it.
And to spend tens of millions of dollars producing something like that? It's a waste. And a shame.