By popularity, by acclamation and by album sales, The Beatles are the greatest musical group of all time. From their early pop work to their later experimental work, they remain the biggest thing in music. Half a century later, their music sounds just as innovative as it did back then.
For diversity, talent, creativity, and magnetism The Beatles are unique among rock bands. They helped to transform the genre into a living entity with many intriguing facets as they explored the music themselves. I shudder to think where rock 'n roll would be today without the Beatles contributions. Even after they broke up, the individual members continued to be significant members of the musical industry for decades afterward.
The Beatles are one of the greatest musical groups of all time. Their influence on pop culture is remarkable. This continues to this day. They have set the standard for years, and groups are still being compared to them. Despite a relatively short time together, they have made a lasting impression on music and society.
Because they are 'the' greatest musical group of all time. In terms of a combination of cultural impact, talent, creativity, artistry, and musicality they are completely unparalleled by any other 'musical group' that has ever formed. The fact that 'art is subjective' is irrelevant because greatness is not defined by any one individuals opinion.
You can't name a band one of the greatest groups of all time because musical taste varies from person to person. To some, yes, the Beatles are the greatest group of all time, but for others, their music just doesn't do it for them. Art is subjective, which makes it pointless to name a greatest group of all time.