Nethack is a turn-based roguelike. Diablo is an action-oriented dungeon crawl (the original at least; I never played Diablo 2 or 3). To me they don't "feel" the same enough to compare which one is better.
I'm a fan of roguelikes too, by the way. If you want to try a somewhat different roguelike for Linux, I recommend Teleglitch (commercial, scifi, quirky graphics, real-time, brutal gameplay).
edit: and Duskers! How could I forget Duskers! For a really different scifi roguelike: http://duskers.misfits-attic.com/
I have a good list here. Nethack, DCSS, the old TOME 2.x releases, SCrap...
I avoid CDDA because I hate games with no clear ending or objectives ingame.
Teleglitch is punishingly difficult from the start, and pretty fast paced too, so maybe give that one a pass.
If any, Flare RPG has anything the first Diablo offers with a longish campaign and a good set of skills.
I know the timing changes everything (and Nethack is more like a text adventure lore made into a top-down RPG), but the environment and tasks ingame aren't so that different both in Diablo and Moria.
There are absolutely differences, some significant. But they have a lot in common.
I would be pretty surprised if, of those who played Nethack around the release of Diablo who also made a habit of purchasing Windows games, there wasn't a majority that also played Diablo.
> I still see no point in saying that Nethack is a better game since it appeals to totally different players.
I agree that the two are sufficiently different, and sufficiently well executed examples of their species, that personal preference between the two is likely to be dominated by the differences that cannot be reasonably labeled "quality".
FWIW, I loved both.
When I discovered libre games thanks to Linux/BSD and some source ports with total conversions, I was sold.
There was 2000 times better quality on a lot IF and now called "indies" than most games since 2002.