Fans have described the Batman v Superman: Dawn of Justice film as "awesome" and a "must-see".
The premiere was held in New York on Sunday evening ahead of its opening this weekend.
Ben Affleck stars in the film as Batman, with Henry Cavill taking the role of Superman.
Affleck was described by some fans as their "favourite Batman" and "the definite Batman.
The film is directed by Zack Snyder and written by David S Goyer and Chris Terrio.
It was conceived after Warner Brothers announced in 2013 their intention to produce a sequel to the Superman movie Man of Steel.
The company later decided the character would instead meet Batman in a new feature film - the first time the superheroes will ever have met in a cinematic setting.
Tom Nolan tweeted from the world premiere in New York, saying: "So lucky to have been at the #BVSPremiere last night and I still can't believe how amazing it was. Not good. Not great. Amazing."
'Crazy for Wonder Woman'
Mariam Chubinidzhe added: "Still not over the #BVSPremiere. Still so giddy. I'm totally going to be seeing this again."
Rodrigo Mariano, who attended Sunday night's screening, said: "I haven't felt this giddy after watching a movie since The Avengers. Goosebumps. Everywhere. Need to talk about it ASAP."
"Lots to process and think about, but overall BvS is an excellent movie," added Ben Kahn.
Others fans were quick to praise the appearance of Wonder Woman in the film, played by Gal Gadot.
"The loudest applause of the night at #BVSPremiere was Wonder Woman's entrance," said Ashley Warren.
Her appearance had been teased in the film's trailers and marks the first time the character has ever been seen in a live-action theatrical film. Film's length criticised
"I was pretty impressed by Batman v Superman. Everyone went crazy for Wonder Woman, she was amazing," tweeted Swati Teerdhala.
But some critics noted the long duration and complex plot points.
Writing in The Sun, Emma Gritt described it as an "insanely long film".
"While die-hard DC Comic devotees might be punching the air as the Justice League are teasingly introduced, the average film fan may be left scratching their head," she wrote.