Genesis likes Greek Tragedy but doesn't have much experience with Shakespeare or anyone other than what I have listed above.
XD okay, I spent a good chunk of the free time over the weekend doing research for that! Here's my recommendation list and why:
Assassins (the Stephen Sondheim musical) -- It's basically a Greek tragedy with extra bonus snark, because of course this is Sondheim. The general idea is that someone rounded up all the people who tried to assassinate the presidents and turned them into a carnival sideshow.
Cabaret -- much more classical musical theater, but still with the dark and twisted slant.
Carmen -- blood, angst, gore, and lots of singing! Plus they literally don't make music like that anymore. (Joudama would have lots more opera recommendations than I do, and I think Gen could really get into opera if he likes the dark side of musicals. Aside from the fluffy romcom operas like The Magic Flute, a whoooole lot of opera is all about spending half an hour singing your dying aria after you've been beheaded. I'm not kidding all that much.)
Wagner's Ring Cycle -- I don't know if this might be a trigger, given that Wagner's telling his version of Nibelheim/Niflheim madness and murder from our planet's legends, over the course of many many many hours.
Madame Butterfly and its variants, including Miss Saigon -- it's Shakespearean tragedy meets the modern era (for various definitions of modern over the years; Miss Saigon takes the Madame Butterfly notion and sets it in Vietnam. And then there's M. Butterfly, where both of the romantic leads are male.)
Les Miserables -- this has more in common with the Phantom of the Opera sensibility than with pure Greek/Shakespearean tragedy due to both stories having been written in the "big whomping five-pound-novel with extra bonus angst" era of French literature, but the music is fantastic.
Into the Woods -- It's a fairy tale with a twist (thank you again, Mr. Sondheim). Starts out light and fluffy and you think it's all resolved at the end of act I -- and then act II happens, and it all hits the fan. It might still end up a bit too hopeful for Genesis, but they do have to go through some major shit to get there.
Man of La Mancha -- not so much about the homicide, but madness definitely plays a big part in it, and the way the world goes and crushes men's souls without a care. But the poor mad fool keeps on trying anyway. Actually, I think you might like Don Quixote's "never say die" attitude as much as Genesis might like the "the universe is a stone cold bitch" attitude.
And here's one I'm recommending for you and Reno rather than Genesis -- Avenue Q. Avenue Q produces songs like "The Internet Is For Porn." And it also sparks off fan parodies like this:
....okay, I think I'd better go see if that HTML chunk works on account of how I've never tried embedding video in a comment before. Back soon! XD