“What makes a successful campaign?”
Glib: I don’t know, but I am pretty sure that the answer lies in The Burning Wheel Codex. Seriously, in the foreward Adam Koebel talks about how he’s gone back to the AdBu* time and time again for advice and inspiration, and hell yes, oh yeah.
Realz: A successful campaign is a game that, for whatever reason, I want to return to week after week. There are a host of factors that figure into this equation, but a big one for me is: “I am invested in the character I am playing and want to know what’s going on in their lives this week.”
Honestly, the last time I felt this as a player was probably the long-running Champions campaign I was in from 2002-2007. Don’t get me wrong, while it was overall a good group, there were lots of incoherent shenanigans going on. Still, the GM created a lot of great Claremont-esque melodrama, and my PC’s life was always interesting.
Granted, basic carrot-and-stick can go a long way; the seven-year D&D 3(.5)e campaign I was in got 20 levels of mileage out of “kick butt amassing power so we can destroy the evil bad guy.” So, there’s something to that.
* AdBu = Adventure Burner, which is now OOP but is contained within the new Codex.