The 41-year-old Swedish-American actor starred as Special Forces officer Rick Flag in David Ayer's 2016 movie - a role he will be reprising in the upcoming "The Suicide Squad".
The film was widely slated upon its released five years ago and, in an interview with Variety, Joel admitted he was also disappointed with the end result.
"I thought the first 40 minutes of the (first) film was f**king great, and then there were conflicting visions and it just didn't end up being what we all hoped it was," he said. "It didn't feel like the movie that we hoped we were going to make, and this is something very different."
As for the sequel, Joel added that the James Gunn-directed movie is a "different universe."
"It just takes it to another level. It's an insane film," he explained. "At the same time, it was very much the movie that I thought it was going to be because the vision was so clear from the beginning. While we were shooting it, it was so clear what we were doing. It's so entertaining. I'm of course hopelessly biased, but I found it to be one of the most entertaining films I've ever seen."
"From A to Z, it's so well paced, it has such a drive and such comedic timing. It's funny along the way the whole time, effortlessly," Joel continued. "But then I think what really surprised me was I was struck by was how well it flowed, but also how he was able to create these little bubbles, these little moments of emotional depth and visual and emotional poetry. And I felt like it really transcended the genre, and it became something bigger."