I started with "La Boheme" (Puccini) when I was about 15. It was also the first time my hair stood on end through music. That definitely got me going:
I agree, "La Boheme" is a great starter opera, as is "Le Nozze di Figaro." Other gateway operas include "Carmen," "Rigoletto," "L'elisir d'amore," "Madama Butterfly," "Cosi fan Tutte," and "Aida," Then there's "Magic Flute," "Faust," and... Puccini's spaghetti opera, "La Fanciulla del West." (Don't be surprised if you recognize a famous Broadway tune in this one.)
I'm not sure any of Wagner's operas are good candidates for a new opera fan, but I'll admit that "Parsifal" was an early favorite of mine and "Die Meistersinger" is one of my all time favorites. If you've got 4 or 5 hours to kill, these operas will do the job properly. Many people recommend "Die Rosenkavalier" as a first Richard Strauss opera, but I would push for "Arabella" instead, even though I've 6 recordings of the former and only 3 of the latter.
Finally, no one ever recommends it, but "Rusalka" is a gem of an opera, rarely produced outside the Czech Republic. I was lucky enough to see a production in Germany in the mid 1970s.
Anyway, welcome to the madness.