Things are becoming less and less sustainable for private servers wishing to deliver fair/classic gameplay. On top of the loss of interest in Conquer Online, the community is over-saturated with buggy, copy-cat servers that close and reopen under a new name every 2-3 weeks. We created a private server advertisements archive for that purpose, but who even finds private servers through epvp these days? Pro4Never struggled with advertising and gaining a community for years. He got into cryptocurrency and made a ton of money, which he then used to get out of the Conquer Online community with. He was more or less unrivaled.
Now, we have a few good classic servers that deserve attention, but they compete with each other. It really thins out the already small player-base for classic private servers. If we're talking about longevity, then I'd recommend

. If we're talking about technical skill and potential,

has peaked my interest. If we're talking about straight up Conquer 1.0 client classic...

offers that. Though, I'm uncertain how long both Legacy and Conquer Gods will last. They're very new servers still - so it could stick around for a while or disappear tomorrow. You never know.