For me it’s Diablo II. Granted I’ve played my fair share of D2 since launch, and also recently on a private server with a comrade from hexbear, but I still feel like years later the game didn’t grab me as much as D1 did.
Granted I don’t hate D2, but for a game that I keep coming back to, D1 takes the prize.
Seriously though a 40K game has the potential to break out of the mire by turning towards the tabletop for inspiration. Imagine if it was kind of like Total War - build and customize your army, have your units gain experience and become elites, have a persistent online league where you can fight for territory with your guild (remember guilds?), etc. Based on how successful Commanders was in Starcraft, I would make a PvE campaign mode the banner feature and advertise it hard to people who like RTS as a concept but don’t go in for competitive PvP.
Personally, I think a campaign interface that’s the Dark Crusade and Soulstorm campaigns combined with aspects of Total War (like unique buildings suited for that province, separate from the main RTS battle buildings) would be ideal. Could expand the scope to be multiple star systems to really get the “grand” scale.
And by guilds, do you mean Avatar Conquest from TW Shogun 2?
Yeah that’s what I was thinking of, it was more interesting than just grinding the ladder IMO.