Rajesh Khanna-Sharmila Tagore is my favourite jodi. Aradhana is of course my most favourite movie. Amar Prem is something like a lovely poem or wonderful piece of art.
Yet i would like to mention SRK_Kajol, Dilip_Madhubala and Amitabh_Rekha too.
As soon as I read your question the first thing came to my mind was SRK and Kajol. And what's this! Many have answered the same thing...... and you too. hahahaha
Some of the most romantic pairs of hindi movies I remember are the following:
1. Shahrukh-Kajol
2. Dilip Kumar - Saira Banu
3. Rajesh Khanna - Sharmila Tagore
4. Rajender Kumar - Sadhna
5. Dharmedra - Hema Malini
6. Anil Kapoor - Sridevi
7. Rishi Kapoor - Neetu Singh
8. Saif - Kareena