This is silly. You guys are all welcome to your opinions on whether P2P or Client/Server is superior, but blanket statements like "Demigod will never be good because it is p2p" is a giant load. I only need to point to this games closest sibling, Supreme Commander, to rule out that whole line of thinking.
These techs both have pros and cons, trade offs and limitations. RTS games have traditionally used p2p systems for a lot of reasons that, when you compare the technologies, p2p is a natural fit for the genre.
Demigod being p2p means that all players always see the same thing on screen. This has good aspects (no warping or client side hacks) and bad (all players limited by the slowest speed, reconnecting is basically impossible). When I'm playing RTS, syncing is a good thing for me. It means I know what I see is always what's really happening. How often does that go out the window in a FPS? "I swear I shot that guy right in the head!" No, you didn't, on his screen he had already moved.
Right now the biggest problem with Demigod and its P2P system is upload bandwidth. That is, many people with fast connections don't realize their upstream is shit. Being p2p, you need to be able to send game state data as fast as you can receive it. That's why larger games get worse because people are hitting the ceiling on those tiny upstream allocations their isps sell. Even worse, if you're sharing your bandwidth with anybody else in the house/dorm, it only takes 1 p2p/torrent app to swallow what little upstream you had to begin with.
Yeah, p2p certainly isn't perfect, but there is a reason it's popular with this genre.