- At least one major fansite mostly devoted to competitive Demigod with replay uploading and commentary as well as active forums (I'm thinking along the lines of AgeSanctuary if anybody is familiar with that)
- A good online matchmaking and ranking system
- Frequent online tournaments which are easy to enter and don't last a very long time
- Developers willing to release balance patches relatively often with big changes when necessary
- A set of well established "pro" players who are active in the community and upload their replays
- 2500+ players online at all times except for late at night
Btw, to the above poster, Demigod becoming a competitive game in no way limits casuals. There will always be a place for casuals to play this game, there's no doubt about it. Barring extreme changes, it's very easy to play right from the start, and it's the kind of game that casuals will probably enjoy playing for quite some time. Casuals will play lots of unrated games in their own hosted lobbies and there will be more than enough of them around to keep that "scene" going. The thing about casuals is, they don't really need a structured "scene" to keep playing. That's why they're casuals....they don't tend to join clans, worry about their stats, or watch replays. They'll be content just playing for fun.
The reason Dota is the way it is, with people in public games having a wide range of skills and many acting "elitist" is because the only reliable way to get a game for most people is to play in public games. This game will have an automated matchmaking system and actual recorded rankings and leaderboards, so the more "hardcore" players won't be mixed with the casuals as much.
I think the best thing the Demigod community can hope for is for this to develop into something akin to the AoE3 community. Not huge, but relatively large, with well-known pros and popular replay-oriented competitive-scene fansites.