I agree. NetHack has heritage (and nerd-cred) going for it--but in terms of raw playability, DCSS has it beat, hands-down. Crawl might also be the most active modern roguelike in terms of development (a rotating cast of a dozen+ active developers working consistently over several years), whereas, to my knowledge, all the modern NetHack forks are the works of lone developers.

For players new to roguelikes, I'd also have to recommend DoomRL (http://doom.chaosforge.org/) as a fantastic game, and its shorter length might appeal to more casual players.