I've seen the 1976 Nagin, starring Reena Roy and Jeetendra as the attractive snake couple.
I recently saw the 1986 Nagina with Sridevi and a besweatered Rishi Kapoor. (And I really need to see the sequel, Nigahen, which stars Sridevei with, well, Sunny Deol. Who I'm sorry to say is no Rishi).
Now, I thought I was Netflixing the 1954 Nagin (the one with Vyjanthimala and the revolutionary electronic score), but it's actually a 1951 Nagina with Nutan. Wasn't paying attention. But how bad can a snake movie be?
Of course, I have high hopes for Hisss, the upcoming Jennifer Lynch movie starring -- yes! -- Irfan Khan (who the IMDB says replaced Amitabh in the lead, which seems very strange). At least I shouldn't mix it up with the Nagin/Nagina family of films, although it might get confused with Sssssss, one of Dirk Benedict's early efforts...