They would still make it big, although probably not on the level as they were in the sixties, where they were like the gods and gurus of pop culture.
A great song is a great song, regardless of era. Lennon and McCartney are the best at what they do.
Regarding experimentation.. hmm. If The Beatles didn't exist in the 60s, other bands would have probably pushed the technical and conceptual limits of music. Bands that come to mind: Hendrix (psychedelic, R&B), Cream (psychedelic), The Who (concept albums, rock operas), and The Doors(psychedelic goth), and the Beach Boys. But they would have done so collectively, not like the Beatles who pioneered most of these things on their own ( with the help of George Martin, of course).