Seriously? That's what's bothering you about shoot'em ups? :P In my experience they're the easiest games to create. Sure, you'll have to work with arrays, while in a text adventure you can get by without, but a text adventure needs a lot more work on the content, and the testing, and the polishing. That it's less technical doesn't mean it's easier.
But the most trouble I had making roguelikes. And the hardest part of that has been... balancing content. Because you have to set up a progression without the ability to place each enemy and health pack manually. But it's still more about the content than the programming.