Holy crap my friend you have asked a huge question. Lemme tackle them.
1. Try something more modern. Moria is alright, but its direct descendent, Angband, is much more awesome. Lots of people play it, and variants.
2. Not many play Moria anymore, if community is important and you liked Moria, then, again, Angband is the ticket.
3. In the last 20 years there have been MASSIVE developments in the Roguelike genre. Many popular games have come out including Brogue, ToME 4, etc...Whole new subgenres have come into being as well. Coffee Break (short style) roguelikes are super popular, there is a 7 Day Roguelike Competition in March where a bunch of us throw together a game in 7 days. Many of those are great. There are shooter games, graphical games, real time games and commercially available games (that cost real money and can be downloaded form Steam). It really has exploded.
I'd recommend checking out Andrew Doull's annual Roguelike of the Year contest results. We are about to have another one, but last year had some great games that are still going strong.
http://roguelikedeveloper.blogspot.com/search/label/ascii%20dreams%20roguelike%20of%20the%20year I would recommend checking out:
Dungeon Crawl Stone Soup,
Angband,
ToME4,
Brogue,
PRIME
and DoomRL.
Also Nethack is still around, with new variants being made like Unnethack and Nethack4.