The funny thing is, I wouldn't call roguelikes like Nethack combat-oriented. The primary sign that a game is combat oriented is when you can only die by enemy hands, thus stating that combat decisions are the only really important decisions you're ever going to make in the game. In Nethack, you can die from pretty much anything, including falling down the stairs because your backpack's too heavily packed. EVERY single decision in the game counts, every decision can make or break your neck. True, the skills are mostly combat oriented, but the gameplay in and of itself isn't, really.
If I get killed by a pink unicorn with a party hat and a clown on a bycicle because I drank an unknown potion that made me halucinate, that's just something you'll never see in a game that cares only about its combat (only God knows what it really was that offed me that day. It was the most hilarious death I ever expierienced).
The procedural nature of most roguelikes, combined with the complexity they usually bring with them, also makes for very great emergent gameplay (that's not procedural storytelling, it's when situations happen to fall together at random to produce an atmosphere, or even a story, of their own).
