God is love
If "God" and "love" are synonymous
If "God" and "love" are synonymous, why are there two separate words for it, not just in English, but in many other languages?
Granted, there are many varietites of love, and many words for them. But even granting that "God" is, say, a specific type of love, or an umbrella term encompassing all forms of love and friendship, this is hard to reconcile with the way the term "God" is used. It might make a certain amount of sense to worship love, or to hope that love will bring an end to war, but why would anyone pray to love, or ask that love cure a loved one's disease? How can Jesus be love's son? How can love make prophecies? Love does not provide an eternal afterlife, nor does it demand praise.
If "God" and "love" are not synonymous
The other possibility is that "God" and "love" are not entirely synonymous. In this case, the phrase "God is love" is at best incomplete, and at worst misleading.