He has a great personality, larger than life, people like him, he's family friendly, etc. But all time for every category of entertainment? That's a stretch, maybe in wrestling. Overall I'd vote Michael Jackson. Jackson was so iconic you could spot his dance moves from a mile away. Even if you just saw his basic shadow silhouette on stage, you'd still instantly know that's Jackson. An absolute legend in music, fashion, singing, dancing and visual art.
But yeah, back to Dwayne Johnson. I can't think of many actors who can compete in 2021. He's definitely one of the most charming famous actors alive right now. I like The Rock, but I get tired of seeing him in like every comedy movie. Likewise, Arnold Schwarseneggar has been in so many movies, you get fatigue watching him all the time. I'd go for Arnold in terms of acting since he's more legendary through the 80's and 90's, which was peak cinema IMO.