I've actually done completely "rule-less" roleplaying with friends online that involved 3-5 people and worked well, but I've also seen some of it go really sour in things like Furcadia.
I've yet to try 4e. I wouldn't mind giving it a try, though I'm a bit hesitant because a lot of the changes don't sit real well with me. I don't mind the step away from Vancian magic (cast and forget), but I hate how they nerfed critical hits and whatnot.
The main v3.5 game I ever run is a custom setting of my own, which has custom mage classes in place of the wiz/sorc/druid/cleric classes and also steps away from Vancian magic. I do prefer to be a player rather than a DM, though. ^_^; My roommate was running a v3.5 Dark Sun game for me, a friend, and my [ex-]boyfriend, but that stopped when I dumped him. ; ;