Very interesting question Brian...
Personally, I think the 60's music (non Gospel and soundtrack) is really up and down in terms of quality. The music recorded at the first post-Army sessions of 1960 was certainly significant if, for no other reason, then to showcase Elvis' new found maturity in terms of vocal ability as well as musical choices. After those sessions, I think his song choices are a bit lackluster, especially the music recorded for the albums POT LUCK and SOMETHING FOR EVERYBODY. There were some excellent songs recorded, don't get me wrong, but some of the songs like FOUNTAIN OF LOVE, IN YOUR ARMS, and IT'S A SIN aren't songs that can be referred to as classic Elvis in my opinion. Again, don't get me wrong, they are decent songs and certainly much better than some of the soundtrack material being churned out during the 1960's, but just ask anyone that isn't a diehard Elvis fan and I will bet they didn't even know Elvis recorded these songs.
The 1963 sessions (commonly referred to as the LOST ALBUM sessions) are above average in terms of song choices, although again there aren't many songs from these sessions that everyone will remember unless you are a member of the Elvis community!!
From this point forward, it is really up and down in terms of musical selections until you get to the cream of the crop...the 1969 Memphis Sessions. Songs like FOOLS FALL IN LOVE and DOWN IN THE ALLEY are clear signs that Elvis was trying to separate his movie music from his non-soundtrack material. His remake of Bob Dylan's TOMORROW IS A LONG TIME is definitely a good choice for Elvis, I think. Of course the Jerry Reed compositions U.S. MALE and GUITAR MAN are often pointed at as the beginning of "The Comeback".
Finally, we have the Memphis Sessions of 1969....classic Elvis!!! Focused, determined, energized....ready to take on the world!!! Nothing more really needs to be said!!!
Obviously Brian, this is only my humble little opinion. In summary I would have to say that there are definitely more hits than misses during the 1960's, although personally I would consider the entire 1960's non-gospel and non-soundtrack Elvis catalog as my least favorite of the 3 decades of music that Elvis recorded.