It may sound crazy, but the sexual activity I miss most (aside from all of them--it's been a while) is the hardest one to replicate alone. Kissing. It's been years since I had a lover who was into getting face-to-face up close and personal the way I am.
I'm all in with the rest of it. Treats from my kitchen, good wine, pleasant-scented oil, happy people on the screen, and end with rest between 1000tc sheets on the most ridiculously comfortable mattress I've ever slept on.
But if great sex is a gourmet meal, soft lips to kiss are home-grown tomatoes.