In the memory Snape gives to Harry, it shows Snape talking to Dumbledore. To show his motives, he displays his (and Lily's) patronus, a doe. Dumbledore, remembering the shape of her patronus, asks "Lily? After all this time?"
Snape responds with "Always." because, yes, he still loves her after all this time, and he always will. He has always loved her.