From the release of It's Not Unusual in 1965 to his current judging role on BBC One's The Voice, Sir Tom has won fans across the generations.
It is well-known he is adored by legions of women the world over, so we canvassed the opinion of some plain-talking Welshmen in a bid to uncover the secret of his enduring appeal.
Former NME journalist Iestyn George describes him as "one of the last surviving stars of his time who still has any kind of credibility".
He partly puts this down to his ability and that he remains close to his roots.
Speaking about his first appearance on The Voice, Mr George said: "When Tom turned up, you were thinking 'how's this going to work?' It should be a bit embarrassing'.
"But it's one of the rare opportunities people have had to see his character and it's made him more of a much-loved figure than ever before.
"He's spent a great deal of his life away from home, but there wouldn't be any misunderstanding about where he's from.
"For me, if you're not authentic or for real, it's just patronising."
Mr George described Sir Tom, who remains married to his high school sweetheart Melinda Trenchard, as "a true professional. There's no side of him, backstage or front stage, there's no pretence".
And he said this extended to his interviews with the media.
"He's really happy to tell the warts-and-all stories, he's happy to tell people 'I've messed around, I've not been great always'.
"I'm uncomfortable with the lovable rogue thing, but what helps people who get away with it is they're not trying to pretend they're anything else.
"Ultimately it's just about being yourself and being very, very comfortable in your own skin."
One of Sir Tom's contestants on The Voice, Ragsy, echoed that sentiment.
"Talking to him, you kind of forget who he is and what he's achieved. His valleys charm kind of comes through," said the rocker from Aberdare.
"The first time I met him... one minute I was thinking 'Oh my god it's Tom Jones, this living legend, this iconic figure'. But within minutes we were just two Welsh people talking about words like cwtch.
"It's his charm first of all and then obviously his God-given talent of having that voice."
Ragsy, whose real name is Gary Ryland, said Sir Tom told him the key to success was confidence.
"He believes in his ability and oozes confidence. He told me I had a powerful voice, but it was that thing of believing in it.
"He still sounds as strong today. He's like the grandfather, the don, of music."
Mr George said despite that confidence, Sir Tom, who is managed by son Mark Woodward, was also good at taking advice.
"The only person I can compare him to is Paul Weller, managed by his father from age 16 onwards," he said.
"He's engineered his own career without any need for representation. They're very different people but there are similarities in the way they represent themselves.
"Tom realises it's tough being yourself, being part of a family unit, in terms of career."
He said it may have been easier for Sir Tom to "do what Tony Bennett's done, tread a fairly narrow path and become that kind of legend of Las Vegas", rather than continually reinventing himself.
Speaking about his Reload project in the 1990s, when he collaborated with a range of music stars from Stereophonics to house DJ Mousse T, Mr George said: "There have been moments, definitely, that are not without criticism musically.
"He's gambled a little bit, enough to make him interesting. He's more than the greatest hits package.
"I think of him as a performer rather than a tortured artist, but that doesn't denigrate him at all.
"There's a simplicity, that's why I struggle to critique his career. I don't think of him in the same way as The Beatles or The Rolling Stones."
Radio One DJ Huw Stephens said, despite reinventing himself, "he's always The Tom Jones, the same man, the same voice, throughout his projects.
"He's not afraid to try things out and work with new producers and also to strip it back and sing those songs he grew up with as a boy in Pontypridd.
"I think it always comes down to the voice. You can tell he's not fame hungry, you can tell he's a very nice man and he just has to sing."
Sir Tom's 75th year was marked with a performance in Denmark on the eve of his birthday and will be followed by another in Iceland the day after.
He marked his 65th with a homecoming concert at Pontypridd's Ynysangharad Park.
Kim Howells, the former Pontypridd MP who is seven years his junior, commented on his peer's longevity.
"He must be the most well-known Welshman that's ever been.
"When I was foreign minister, I literally travelled everywhere in the world and wherever I went and said I was from Wales, people would say 'Tom Jones.'"
Mr Howells, who also grew up in the south Wales valleys, said: "I think the songs he sang were different, but he sang them almost like a blues singer and that stayed with him.
"That ability to swing stayed with him and to add a gravity to whatever it was that he was singing.
"His first hit, It's Not Unusual, was a very catchy tune. He had a kind of animal power to him in the way he sang, the way he moved, a bit like Elvis I suppose.
"I think that first generation of fans stayed with him. I think he's managed his career very cleverly as well. He never entered into areas which were an embarrassment to him."
So is there any sign of Sir Tom slowing down as he reaches the milestone of 75?
"I think he will sing until he dies," said Cardiff-born Mr Stephens.
"He's got a hard-work ethos and I think he will sing until the end."
Sir Tom Jones celebrates his 75th birthday on Sunday and the appeal of the Welshman is as strong as ever.