i think priscilla was the love of his life, and the 3 womans that elvis loved were his mother , priscilla and lisa.
Many people said that elvis was forced to marry ( wich i believed pris's father did) but because elvis make a promise when he wanted priscilla in graceland so he took that choice.
And also if you listened all his songs made after the divorce all said about a separation, that he loved (always on my mind, separate ways, it's over...)
And if you had the concert desert storm you will listen that elvis really loved her and he didn't even care that much Sheila or linda (because i believe in 74 he was with the 2) , in this concert were priscilla, lisa and Sheila , and Elvis in the song It's midnight in the middle said " listen Cilla" and he also talked about how much they loved and take care of each other , that they were friends and then he said some comment on mike stone.
So for me cilla was the love of his life