If any movie is critic-proof, it is Avengers: Endgame, the culmination of 21 previous titles in the wildly popular Marvel Cinematic Universe, which began with 2008’s Iron Man.

Pre-sale records have already been destroyed by the cinematic colossus, with the film, which is released on Thursday, selling more advance tickets in its first 24 hours than any other title in history, as even lukewarm aficionados of the franchise race to watch the film on its first weekend, before spoilers assail them.

Yet immunity to bad reviews has proved academic: a slew of five-star write-ups met the official lifting of the embargo on Tuesday night, with the Guardian’s Peter Bradshaw among those declaring the film a fitting, satisfying – and surprising – final fling.

Avengers: Endgame holds a 96% approval rating on Rotten Tomatoes, and word from cinemas is that both loyal devotees of the franchise and fly-by fans exit happy.

Angie Han wrote on Mashable: “At both the screenings I attended, the audience reactions were so loud at certain points that entire lines of dialogue were swallowed up. Which is probably just fine with Marvel: all the more reason for fans to go back and see it a second time.”

Even the New York Times was susceptible to its charms, calling the denouement “like the encore at the big concert when all the musicians come out and link arms and sing something like Will the Circle Be Unbroken. You didn’t think it would get to you, but it does.”

So keen is the appetite for the film that predictions for the opening-weekend haul hover around $850m (£657m), and it looks certain to take more than $1bn in less than a week of release.

In the US, the film will open in 4,600 theatres – the widest release ever – and is on course for a series-best domestic opening-weekend box office of around $300m. The territory that should nudge it over the $1bn mark so soon, however, is China, where the film opened on Wednesday, making more than $100m in its first 12 hours. It is predicted to take at least $250m from its opening weekend.

The previous film in the series, Avengers: Infinity War, made almost $200m in China, where it opened a fortnight later than in most other countries. That movie currently holds the record for the biggest worldwide opening in history, with $640.5m.

Shot back to back with Avengers: Infinity War by the same director siblings, the Russo brothers, Avengers: Endgame unfolds in a landscape destroyed by the catastrophe that dominated the previous film, with heroes including Tony Stark (Robert Downey Jr), Captain America (Chris Evans) and Thor (Chris Hemsworth) wracked with grief.

Its running time is just over three hours, which appears to be welcome news to punters wanting bang for their buck, but bad news for cinemas, which have had to clear other screens for additional showings of the film.

Most other studios have avoided releasing films at the weekend for fear of competition, and even the previous fortnight has been strikingly light on major titles. In the US, domestic takings are down 17% year-on-year, while in the UK the unseasonable Easter sunshine contributed to a holiday haul down 51% from the previous weekend.

The positive notices and expected takings for Endgame mean the bar is set even higher for Star Wars: The Rise of Skywalker, the ninth and final film in the cycle, started by George Lucas in 1977. That film opens at Christmas, and is also a Disney product, after the company purchased the rights from Lucas for $4.05bn in 2012; it bought Marvel for a similar figure in 2009.

After acquiring 20th Century Fox last month for $71.3bn, Disney has now regained the rights to further Marvel characters, X-Men and Fantastic Four, making it the owner of all major cinematic franchises bar the DC universe.

• This article was amended on 25 April 2019 to correct the figure of $850,000 (£657,000) to $850m (£657m).