The best I ever had was with a girl I never even penetrated. We hadn't known each other long, but of an evening we hung out at my place, had a few drinks and talked for a couple of hours, when she suddenly decided she wanted a kiss. So of course, as the gentleman, I kissed her very gently, and somehow this became an intense experience between us.
Shortly it lead to the bedroom and before long we were naked on my bed. It was like she was on fire, like she was burning up and her thirst could only be quenched by me. She aroused me in an epic way; she whispered hot, sexy things to me, she licked and kissed and suckled me everywhere as I did the same to her. She teased me...oh god, what seemed like for a hundred years, sliding herself along my length, and I reciprocated in kind with long, sweet licks and sucking.
The feeling was like...she made me feel like I was the center of her whole universe, and for those couple of hours she was absolutely the center of mine. The closest we came to penetration was right at the end, when the head of my cock tucked between her lips and she erupted into the most intense orgasm I think I've ever felt a woman have. I could feel her trembling and crying out and pulsing and squeezing...and I lost it and filled her with cum.
This, of course, lead to a pregnancy scare for which neither of us were ready, and somehow once it was resolved everything else crumbled. We played a couple more times, but we never got to full penetration. She was amazing and beautiful and thick with a tight body, beautiful eyes, an amazingly sexy accent and a passion that I've never felt before or since.
Yes, that was the most amazing, the best sex ever--and I regret that I didn't take more care to try and nurture that experience into the amazing relationship I know it could have been.