"Thank you". If you want to go further, "that's nice of you but I don't believe in superstition", "but I appreciate your good heart and loving wishes".
I like this one from The Big Lebowski, "Nobody fucks with the Jesus!"
I remember hearing a preacher in church tell the congregation that when God comes to you, he usually comes to you through people. Now it's true that inscripture he does, but it's also very common in the Bible for God to show up and slap some bitches for their disrespect.
My advice would be to use logic and be nice about it. Although they're being presumptuous, annoying and naiive when they say "Jesus loves you", I think it's more effective to get them to think about their reasoning rather than just piss them off. That way you have the chance to bring them to reason instead of polarizing them further into their own faith.
"Why doesn't he tell me himself? Why doesn't he come down to earth, sit with me in the darkest hours of my life, through the loss of friends, the pain of grief, the death of loved ones, the genocide of my countrymen, the injustices of our time, and comfort me? Why doesn't he answer all the questions I asked as a child when I believed he was there? When you talk to him next, ask him that. I'll believe in your god when He gives me a reason to. Not you."
You can shorten it if you want, just an idea. People telling me Jesus loves me is especially offensive to me because I value love so dearly, and think it should be respected as a verb, not just a feeling. So when people tell me Jesus loves me I rage at them for comparing Jesus to the love of my father, mother, friends or girlfriend, who have shown me more love, care and reason to believe in love than Jesus ever has.
Believers' yap about their savior working through others is one of the biggest dodges I've seen in their playbook, and I'm in complete agreement about demanding a removal of intermediaries. People can love, aid and support others with no more belief than in that action as a means of "raising all boats." I frequently help others for no other reason than I LIKE to help others. Nothing else has anything to do with my action, least of all some insubstantial deity.
If some god wants to express his/her/its appreciation for me, it can do so in person and without all the mumbo-jumbo. Those acting as putative intermediaries can either give me one hell of a good reason to believe their not just acting on their own behalf or get summarily dismissed. I have a low tolerance for bullshit, and this is bullshit of the worst sort.
The best response: "Whatever".
Ask them to "Ankh if they love Isis"
And yet another response:
"WHY would I care that some guy who died 2,000 years ago loves me?"
A semi-serious response might go like this: "If Jesus loves me unconditionally, then where is the benefit in becoming a Christian? If on the other hand the love of Jesus is contingent on my assuming a particular stance, then how can salvation genuinely be a free gift?"
I'm almost positive that the "unconditional" stuff is not in the N.T.
Jesus has a lot of conditions, most of which his followers ignore.
If you gotta react, OVERREACT! Nothing succeeds like excess!