KISS was my first concert, and I bought every album up until the "solo" albums. I was 13 at that concert, and it blew my mind.
After YEARS of rocking, I would say KISS has the following REALLY GOOD songs:
Goin' Blind
Strange Ways
Black Diamond
Nothing to Lose (although I cringed when I realized what he meant by "thought about the back door" and the overall point of the song)
Let me Go, Rock and Roll
She
Rock and Roll all Night (although I wouldn't care if I never heard it again)
Detroit Rock City
Beth
Hard Luck Woman
and for me, that's it. I think the rest of their catalog is pure crap, and I mean REALLY REALLY ANNOYING BAD CRAP.
So for MY taste, (and I realize taste is subjective,) KISS has 10 good songs on 20 or so albums.
The Beatles have less than 10 BAD songs on well over 20 albums, depending on how you count them.
And the Beatles have composed some of the greatest songs in the history of rock and roll, both as Lennon/McCartney, Harrison (in the Beatles,) and Lennon, McCartney AND Harrison as solo artists.