Well, after leaving this fallow for a year, let's pick things up again.
Currently running Dungeon Crawl Classics six players. It has been a long time since I've had six gamers in a campaign at once -- but through strange machinations we have three couples playing. These days groups of three to five have been far more common, with four players being the mystical 'sweet spot' for a game.
But if there has ever been a sort of game that would handle six players, an old school game would be it.
I'm really in a Dungeon World head-space right now, though. Lots of "discover through play" and "share the narrative with the players" ideas floating through my head. But I don't see that as a bad thing at all.
The current game is modelled roughly on the Adventurer, Conqueror, King System game I ran on rpg.net a year ago or so. Roughly, because I've chosen "Late Antiquity" for a time frame and "Fort Salvum" as our point of civilization on the haunted and perilous frontiers of the sudden and catastrophically collapsed empire.
However I'm placing Greg Gillespie's Barrowmaze close by, and a couple other odds and sods, so we'll see where this actually goes.