Some quotes on cultivating Love across some religions, spiritual systems, and traditions...
"Cherish others as you do yourself." -Je Tsongkhapa
"Cherishing others is the source of all happiness." -Lama Zopa Rinpoche
"Love others as I have loved you." -Jesus
"My religion is kindness to all." -The Dalai Lama
"Now do not think of anything other than the welfare of all beings." -Shantideva
"In a world of endless questions, love is the only answer." -Matt Kahn
"Love until it hurts." -Mother Teresa
Thoughts and opinions...
I believe Buddhism has some of the best methods for cultivating Love, like Serlingpa's 7 Cause and Effect Trainings and Shantideva's Exchanging Self With Others and Theravada Loving-Kindness meditation, but other religions have their ways of cultivating Love too.
Emptiness makes Buddhism uniquely Buddhist. Other religions are useful for cultivating Method for people of various capacities. Their obscurations are so great that they can't begin to understand Emptiness. My wife, for example, doesn't "get" it at all. She's a Christian and is one of the most loving and ethical people I've ever met. For her and her capacity, her religion is a perfect fit, and maybe in a future life she will have the capacity to practice Buddhism.
(I'm not saying "capacity" with any sense of belittling. I'm stating it as a fact. You can increase your capacity to understand Emptiness with a lot of effort. We are all compounded entities capable of increasing spiritual capacity through right effort. It took me 16 years to understand the Gelug view of Emptiness.)