I ADORE Pretty in Pink but I came here to post that their kisses were my least favorite in movie history. I think Andrew and Molly had chemistry but I don't know if he doesn't know how to kiss or what but it looked awkward to me.
My favroites have mostly been mentioned: Winona Ryder had great chemistry with Ethan Hawke (Reality Bites), Christian Slater (Heathers) and Michael Schoeffling (Mermaids) - movies full of good kisses!
Rachel McAdams and Ryan Gosling have top-notch chemistry - their kisses were incredible in the Notebook. I didn't like that movie at all - they MADE it for me.
I'll echo others on Amelie, Say Anything, GO (Claire and Todd) and Cruel Intentions.