Probably the easiest opera for an opera newbie is Puccini's LaBoheme. This is easily one of the most beautiful, easily assessible, melodic, sad, etc etc opera's, ever. Great duet's. Just turn up the volume and settle in. :-)
I am not an opera fan...but...
Disclaimer---I am not much of an opera fan. However,I get the occasional jones for an opera fix or at least the feeling that I should be trying to like it. (Especially when I'm in my "godfather" mode) I recently bought a CD entitled "Simply the Best Night at the Opera. This one satisfies my needs. It is great.