My wife hates how many of my jeans are saggy in the butt, and I don't love it either, so recently after another comment from my wife - and I'm dead serious here - I Googled "jeans for tall guys with no butt" and immediately found The Perfect Jean.
I'm a 6'6" 50 year-old dude with a minimalist butt and I've always struggled to find jeans that fit right. I bought one pair of these to test, and after wearing them for 5 days straight (yeah maybe that's gross, but it's for science!) I'm about to order more. They look great, and are SO comfortable, and saggy butt? NOPE. There have been several times getting into/out of my car when I was SURE they had ripped from crotch to butt, because there's just no way jeans could move with me so gracefully, right? WRONG. No rips, just amazing flex.
I can't say how they'll hold up over time since I've only had them for a week, but I can't over-state how happy I am with the comfort and fit.
EDIT: The order page suggested sizing down on the waist. I typically wear 36W/36L and ordered these in 34W/36W and they're perfect.