Sorry if this doesn't count.
When i played the Sims 2 today, i noticed the game coincidentally played all of my favorite OSTs in a row (brick sim, arch of the sims, arch of the sims adam freeland, arch of the sims nick frageland). Also, the game never blue screened. That's what made me go Awww.

(i thought to myself... "Although The Sims 2 is not a human being, could this be the game trying to tell me 'I Love You'? Maybe video games have sentience after all?". Well of course, The Sims 2 is just a video game with no sentience whatsoever, but i had a silly thought about it. I like to think this is The Sims 2 telling me "I Love You". Well... Sims 2... I love you too!)

Couples cuddling under the clouds/stars, especially if they do so autonomously.

My most favorite romantic interaction by a big margin. Most other interactions I would rather interrupt, but cuddling like this, I won't hesitate to take snapshots and let them enjoy their sweet moments together.