Troy Baker and Ashley Johnson are sitting on a sofa in a luxurious suite of a five-star Mayfair hotel. The balcony doors are wide open, scorching rays of sun stream in but there is a welcome breeze. Brought in to interview them, my every utterance is diligently noted by a media officer. My time with them will be strictly limited.

If you are wondering who Baker and Johnson are, you have clearly never played the popular blockbuster game The Last of Us. Their strong, emotional vocal performances as the game's leading characters, Joel and Ellie, have made them two of gaming's most critically acclaimed actors, and while neither of them like to admit that they have been elevated to star status – "Why don't I have sparkling water?" booms Baker, laughing – there is no denying that voice acting in games has come a long way.

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The days of games peopled by melodramatic characters delivering disjointed monotone lines, peppered with awkward silences are gone (give or take the odd French or British actor trying to affect an American accent in 2010's Heavy Rain). Games such as 1996's Resident Evil would build suspense only to shoot it to pieces the moment a character spoke. "That was too close," Barry barks at Jill. "You were almost a Jill sandwich." A character from House of the Dead 2 from 1998 was so bad he was described as having as much emotion as a cheap text-to-voice program.

Shape Created with Sketch. The Last of Us Remastered Show all 7 left Created with Sketch. right Created with Sketch. Shape Created with Sketch. The Last of Us Remastered 1/7 Joel and Ellie in Pittsburgh 2/7 Stealth through a car maze in Pittsburgh 3/7 Sun over Lincoln 4/7 Joel hides from hunters 5/7 Joel and Ellie in the woods 6/7 Hunter fight 7/7 Clicker screeches 1/7 Joel and Ellie in Pittsburgh 2/7 Stealth through a car maze in Pittsburgh 3/7 Sun over Lincoln 4/7 Joel hides from hunters 5/7 Joel and Ellie in the woods 6/7 Hunter fight 7/7 Clicker screeches

Today developers understand that terrible vocals can be woefully distracting and if games are to be on a par with film for narrative storytelling, actors need to be on form. Had The Last of Us, released in 2013 for the PlayStation 3 console, and widely praised for the quality of its writing and storytelling, been poorly voiced, the chemistry between the characters would have suffered. The game is set in a post-apocalyptic world where an infection has all but wiped out the human population. Joel's job is to smuggle the 14-year-old Ellie out of Boston's quarantine zone. Of all the things being altered for a remastered, visually re-tooled version for the PlayStation 4, the sparkling delivery of the protagonists' lines is not among them.

Voicing a video-game character today is a prestige job rather than a chore one of the production team might be cajoled into doing at the end of the process. Baker sees it as another branch of acting and sees no stigma. "I'm an actor," he says. "The qualifier of 'voice' actor is like saying I'm a 'foot' walker: of course I use my feet to walk."

Johnson, who has worked on many television series including CSI, The Killing and King of the Hill, is equally defensive: "It's not a lesser form of acting in any way. It's harder in some ways because you can't use your eyes. You need to get your emotions through your voice. It's challenging."

It certainly is, thanks to the modern way of producing huge action-adventure games. Although many voice actors in games and animation stand behind a microphone to deliver their lines, those involved with The Last of Us physically acted out their scenes which were then motion captured. This, says Baker, made the production "the perfect marriage between stage and film".

"You have this theatre of the mind and you don't worry about where the camera is because you are being shot in a 360-degree space," he continues. "You get to have these very quiet, subtle and nuanced performances."

One such performance proved particularly difficult. Baker was acting out the scene in which Joel's daughter, Sarah, dies. The game's director, Neil Druckmann said Baker "invested so much of himself into that scene. Between takes, he was really crying and he'd have to leave for a few minutes and come back." Baker has called it one of the most difficult days of his life. "Games have great depth," he says. "I was aware that when Bruce Straley and Neil Druckmann were writing the script, Neil had just become a father and that was really the impetus of where this entire story was born from. His world had changed. We began fantasising about what it would be like to lose someone you love. It wasn't easy."

Challenges aside, there is a good living to be made voicing games. Jennifer Hale has acted in more than 130 video games since 1994. Ed Boon has voiced Scorpion in every iteration of Mortal Kombat since its 1991 debut (he holds the world record for longest-serving voice actor). Nolan North, whose major role is Nathan Drake in the Uncharted series, has voiced characters in more than 100 games. Kerry Shale provided individual voices for 32 characters in Dog's Life on PlayStation 2.

Now Hollywood actors are getting involved too. Elijah Wood, Gary Oldman, Dennis Hopper, Christopher Walken, Samuel L Jackson and Liam Neeson have all voiced video games recently. Ellen Page lent her voice and face to the protagonist Jodie Holmes in Beyond Two Souls, the script for which stretched to 2,000 pages. Kiefer Sutherland is playing Solid Snake and Naked Snake even though David Hayter voiced them in every release of the Metal Gear Solid series from 1998 to 2010.

Are games just another way for actors to earn cash? Baker recalls Annie Wersching, who has appeared in 24 and Bruce Almighty, walking on to the set of The Last of Us: "She was like, 'this is incredible'. We also had Merle Dandridge who has done so much theatre and TV, like The Newsroom, Sons of Anarchy and The Mentalist. She said, 'I haven't been able to stretch these muscles in so long.' They love it."

Yet there are some who fail to understand. "When we were auditioning for The Last of Us, there were a few people who had worked in TV or film," says Baker. "One said, 'I'm not sure what you want me to do. If this was TV or film I'd give you emotion and stuff like that. Do you want that?' The director, Neil Druckmann, said, 'Yes, do that. Treat this with the same amount of respect as anything else."

Video-game roles require dedication. The Last of Us took three years to make. "You become very attached to the characters over that time," says Johnson. But not so much that she would play Ellie in the forthcoming film version of the game, which will be directed by Sam Raimi. "I'm not 14 and that's one of the things that makes Ellie who she is," Johnson explains. At last week's Comic-Con, Game of Thrones' Maisie Williams (Arya Stark) was mooted as a possible Ellie.

Movie versions are a different ball game. For every Prince of Persia hit there is more than one Super Mario Bros flop. Baker hopes film actors will portray the characters with respect. "You never truly own a character, you are merely a custodian of it. I just want the actors who portray Joel and Ellie and all of the other roles to get it and to understand it," he says. It's for film actors to mess up now.

'The Last of Us Remastered' is released tomorrow