Iron Man was released in theatres worldwide on May 2, 2008, with no one knowing that it would forever revolutionise the film business. Although plans for a connected universe starring Marvels lesser-known superheroes were already in the works, viewers were unsure what to expect from the film directed by Jon Favreau, known for his comedy works, and starring Robert Downey Jr., an actor untested on such a grand scale.Robert Downey Jr. as Iron Man (Image: Twitter)Despite this uncertainty, the picture was a huge hit, getting excellent reviews and making about $600 million worldwide. It was even listed as one of the best ten films of the year by the American Film Institute and won two Academy Awards nominations. By adding the film to the United States National Film Registry by the Library of Congress last year, the government itself has also recognised the cultural impact of the Iron Man series.Iron Man and the beginning of the Marvel Cinematic UniverseIron Man was far from a sure thing, and it wasnt even the most expected superhero film of the summer when it debuted. Only two months later, another film titled The Dark Knight was set to hit theatres, giving audiences their first Batman-Joker clash since 1989. As the film celebrates its 15th anniversary, coinciding with the Marvel Cinematic Universes 15th anniversary, its worth looking at the impact Iron Man has had not only in Hollywood but also in India.DCs The Dark Knight Trilogy (Image: Twitter)Following the release of the first Iron Man film, a post-credits scene featured Nick Fury informing Tony Stark about the Avengers Initiative, kicking off the franchises first phase, which featured the debuts of Thor, The Incredible Hulk, Captain America, Black Widow, and Hawkeye. These characters were the main squad in the 2012 film The Avengers, which made $1.5 billion worldwide. The acquisition of Marvels rights by Disney enabled the series to grow beyond theatrical releases and into television and streaming.Avengers (Image: Twitter)The Marvel Cinematic Universe is currently the most profitable movie franchise of all time, with $28.7 billion earned across 31 movies globally. As many as 10 MCU movies have grossed more than $1 billion at the box office, with Infinity War and Endgame grossing more than $2 billion worldwide. Iron Man 3, which came out only five years after the first picture, made $1.2 billion globally.The impact of Marvel Cinematic Universes huge success made Competitors start creating their own shared universes. With 2013s Man of Steel, Warner Bros. was one of the initial studios to follow in Marvels footsteps, launching their own interconnected DC film universe. However, due to a lack of clear direction and an evolving plan, the franchise has struggled and is currently undergoing an extensive restructuring with new management. Other shared theatrical universes, such as James Wans Conjuring franchise and the MonsterVerse starring Godzilla and King Kong, have proven successful for Warner Bros. Universal Studios Dark Universe, which attempted to gather old Universal monsters together, failed after only one release, The Mummy in 2017.Image: TwitterThe Indian cinematic universesIn recent years, India has developed more shared franchises than any other film industry. Despite being late to the game, Indian filmmakers have established successful shared universes, including Dinesh Vijans horror-comedy universe, Prashanth Neels cinematic universe, Lokesh Kanagarajs cinematic universe, Raj & DKs The Family Man universe, Rohit Shettys cop universe, and YRFs spy universe are some among them.