Miles Davis once said that the hardest thing for a musician is to sound like yourself while playing within a group. George struggled with this as a vocalist and a soloist, but mostly as a songwriter. Here's a complete list of the Beatles songs he wrote:
George, whose voice is perhaps the most imitable of the four Beatles, sang lead on some of the covers in the band's oeuvre, including Devil in Her Heart by the Donays and Roll Over Beethoven by Chuck Berry, and Everybody's Trying to Be my Baby by Carl Perkins. He reliably sang a second harmony part on many Lennon/McCartney tunes, though never the highest.
As noted above, George was responsible for introducing Indian instruments such as the sitar and tabla into the Beatles' western song structures, and thus to the entire pop music audience of the western world. This happened even before the heavy Indian textures of Love You To, on a Lennon/McCartney composition called Norwegian Wood (This Bird Has Flown). Impressed by the music of Ravi Shankar, George had bought a sitar and taught himself to play, and he used it to give an ethereal tone to the song's melody.
Long after he'd made sure that all his Beatles compositions had a unique feel--say, 1966 or so--he still loved to express himself in old-school rhythm and blues terms, and no one could doubt that he had the best chops of the three axe wielders. Listen closely to The End at 0:53. That's Paul, George, and John, in that order, trading four-bar solos. Note how George mostly sticks to the upper register and demonstrates his note-bending skills, while Paul can't not be melodic and John just wants to make a lot of chunky noise.
George made a cameo appearance in The Rutles, Eric Idle's 1978 TV film that parodied The Beatles, and the two became friends. When financial backers pulled out of Monty Python's Life of Brian due to controversial "blasphemous" material, George stepped in and contributed millions in completion funds through his production banner, Handmade Films, which he formed for just that purpose. He claimed to have an interest only in seeing the finished picture, as he was a big Python fan, but the film was enormously successful and Handmade went on to produce 23 other British films in the 80's, including Nuns on the Run and Time Bandits, which launched Terry Gilliam's non-Python career. So, if not for George's help, there would probably be no Brazil or Fear and Loathing in Las Vegas. Just another indication of the karma he taught us all about. We'll miss him.