Short Version of This Post:
Two-player-1-GM games usually feel suboptimal but if both players are in control of multiple PCs, it's really fun. So if you;ve never done it, I hereby recommend trying it next time you've only got 2 players.
Long Version of This Post:
It's odd: you can play Monopoly with 3 players and it feels like you're really playing, you can play chess or 40K with two people and it's feels fine, but somehow playing an RPG with just one DM and two players always seems a little too quiet to me.
I've had many fun games with two players (including, most recently, an unfortunate but diverting episode involving Ghost Monkeys & Draculasers courtesy of Ben A and Forrest H ), but in general I would always take a third player if offered one.
So's: Last night/this morning Arcadayn ran two of us through a beta version of Goodman Games' new Dungeon Crawl Classics game.
If you haven't heard, a distinctive feature of this PostRetroClone is the "adventure funnel"--each player starts with 2-4 zero-level classless schlubs with naught but stats, a few cp worth of items, a randomly rolled profession, no armor, and second-rate weapons. These luckless citizens then are run through an adventure, some of them probably die, and then each player turns one or more of his or her surviving schmucks into a "real" PC with a class and everything in time for the next adventure.
My take on this whole idea is it seems pretty fun if you've got time to do that. It might be kind of a pain if your first session has like 8 players in it.
My most powerful impression from this session, though, was that for a two-player game multiple PCs seemed like an ideal and well-thought-out idea and just Goldilocks right.
We each took 4 bare-bones Joneses with names and jobs and took turns deciding whose guy would open the next door. Having 4 PCs, you start out thinking one or two of them (the ones with the especially average stats) are kind of expendable, but after a while you begin to like them all. Like: Oh, hey, this guy has a +1 to dex, maybe he'll climb up the statue.... And then hey, Mr 13 Dex is now a local hero at the table for ten minutes.
You use your guys like a skirmish wargame, but the density of interaction is enough that, even in a one-shot, they begin to develop identities and quirks and specialties. Maybe it was just the quality of my fellow dungeoneer, but the complexity of possibilities you generally feel in an 'ordinary' game was there--it felt like we were playing a "full" game the way it was meant to be played--as if 2-player D&D were as natural as 2-player ping pong.
It wasn't like having henchmen or hirelings either--who, at least for me, usually just feel like light-entertainment at best or a pain in the ass to keep track of at worst. These guys were totally "ours"--unike hirelings, making them open the spooky skull-head door was not automatically a sign of contempt.
So, anyway: whether or not I'm using DCC or the "funnel", next time I can only rustle up two players, I'm gonna have them bring along some extra PCs and see how it goes.