They've influenced more artists directly and indirectly in the history of music, and have continued to do so.
Sure.... many of the artists mentioned here influenced others indirectly and directly, but how many have continued to influence throughout the years?
Not as much as the Beatles have.
How many artists are still strongly and directly influenced by The Byrds? or Dylan? or Beach Boys? or Funk Brothers? or even James Brown?
We might find an artist here and there that say they have, but then those same artists will say their 'major' influence was the Beatles. Artists are usually influenced by an array of other artists, but The Beatles are usually the artist's main influence and they continue to be so.
No, they're not. The Beach Boys, Motown and James Brown have just as good as an argument than the Beatles.
No, they really don't.
The Beach Boys...or at least Brian Wilson... are personal favorites. But they readily admit that they chased the Beatles as the measuring stick all throughout the 60's. Their international appeal lasted a very short period of time, mostly because of the Beatles stranglehold on the charts and the public.
Motown isn't a musician or a band.
James Brown had nowhere near the commercial success, nor the longevity at the top of the game, that the Beatles had.
All were influential. None were remotely close to having the influence that the Beatles did.
People like to be contrarian and interject personal preference. The Beatles changed fashion, hairstyles, attitudes, social mores. Spoke about relevant topics in an era before musicians were afforded that luxury. Owned their own music and publishing rights, again when that wasn't the norm. Wrote, sold and are played more than any other two artists combined.
Everyone was influenced by someone. Nobody's influence was as far reaching or long lasting.