I started listening to opera with Wagner, but he really isn't the best place to start. I'm still trying to figure out ("get into") the ring cycle, and I've owned the complete Karajan recording for four years now.
A better beginner opera that's still rewarding years later is Bartok's Bluebeard's Castle. Rather than being shackled by the libretto, the music is very expansive, with lengthy purely instrumental sections. The story only features two characters, and the staging is fairly simple (seven doors and colored spotlights), so the whole thing is driven almost entirely by musical rather than visual or verbal aspects. It's also a great deal shorter than most operas (it all fits on one disc), which makes it fairly accessible to someone who is more into symphonies and sonatas than opera. I've listened to it at least once a day for the past month or so, and I still find something new in it every day.
I haven't checked out the recording posted here in Audiofile, but
this recording is really well done. I'll upload it in a bit, but I'd recommend actually purchasing the recording to get the full effect. The booklet is very informative and interesting, and helped me understand the piece a lot more.