The key to successfully using CGI is to at least semi-convincingly integrate it with everything else, a task that many, many movies have failed to do over the last few decades. So let's take a look at some of the worst offenders.
"The Lawnmower Man" (1992)
This Stephen King adaption is the very definition of "ahead of its time." At least in the sense that everyone involved should have known there was no way they could possibly render this virtual reality environment in a way that looked good back then.
"Star Wars Special Edition" (1997)
George Lucas, amusingly, got it into his head that the problem with the original "Star Wars" trilogy was that it needed CGI, and also that the technology of the mid-1990s was good enough to finally fulfill his original vision. And so we, for a few years until he updated it again for the DVD release, had to live with this incredibly horrible CGI Jabba the Hutt.
"Air Force One" (1997)
This one holds a special place in my heart because it comes at the end of a movie that was very light on CGI up to that point. And then, suddenly, that happens.
"Harry Potter and the Sorcerer's Stone" (2001)
There was a whole thing in the early 00s where fantasy movies would have real humans ride on top of not the most convincing CGI creations. The bathroom troll gets bonus points because the lights flicker throughout the scene, making it look somehow even more fake.
"The Mummy Returns" (2001)
I put this one last because it's probably the most offensive of all the movies on this list. Casting Dwayne "The Rock" Johnson as the villainous Scorpion King is a great idea. But "The Mummy Returns" is the only movie that has managed to make him look ugly. And it's hard to forgive such a thing.
"Die Another Day" (2002)
The '90s and early aughts were a magical time because of all the filmmakers who really thought that the technology of that moment was good enough that they could pull off any crazy stuff they could imagine. But they were very wrong, and this sequence where James Bond falls off a glacier and wind surfs away is a testament to the folly of those years.
"Star Wars: Episode II - Attack of the Clones" (2002)
Could honestly do a whole list of the goofiest CGI just from "Star Wars" movies, but this part where Anakin tries to surf on the back of this herd beast on Naboo is an all-timer.
"Freddy Vs. Jason" (2003)
This slasher mashup was not exactly a major-budget affair, so the dopey CGI on this part where Freddy Krueger turned into a weed-smoking caterpillar isn't too much of a struggle to get past. But it does look really, really bad.
"The Matrix Reloaded" (2003)
As was the case with "Star Wars," the Wachowskis' ambitions for the "Matrix" sequels, and "Reloaded" in particular, definitely outpaced what could actually be convincingly delivered. And so what is ultimately still a very fun sequence (Neo vs a hundred Smiths) ended up the butt of jokes for so many years after the movie came out.
"A Sound of Thunder" (2005)
This really awful movie will always be one of my faves because it managed to have an alleged $100 million budget yet still look as cheap as any random thing airing on the Sci Fi at the time.
"Fantastic Four" (2015)
The behind-the-scenes drama on this flick involved, reportedly, the director being fired during production and half the movie being rewritten and reshot. And, like with "Justice League," the CGI generally ended up looking real rough. There are parts that look like they would have been at home in the previous "Fantastic Four" movies from more than a decade earlier.
"Avengers: Age of Ultron" (2015)
For the most part, the CGI in this "Avengers" sequel was as good as it needed to be. And then Iron Man would pop into a scene looking like a test render from the original 2008 "Iron Man" flick.
"Justice League" (2017)
We probably all know the story by now. Henry Cavill had to pop in for reshoots while "Mission: Impossible - Fallout" was still in production and couldn't shave off his facial hair. Warner Bros tried to CGI out the mustache, but it was not at all convincing and ended up honestly being really hilarious.