Ok: so where am I?
Yet another example of variance: a strategy game that uses die rolls to determine outcomes of battles is higher variance than a strategy game that does not.
Somebody out there might be saying, "*I* can beat the first boss in Ninja Gaiden every freaking time. It's not such a high variance game." What I mean is - (wishing my blog could support graphics right now) - if you were to graph the probability of succeeding a challenge against player skill, a low variance game would show a steep jump from 0% to 100% when player skill reached a certain point, whereas a high variance game would show a gradually increasing slope. My Ninja Gaiden skill puts me at around a 10% success rate against that first boss - yours may put you near 100%, but that doesn't mean it's a low variance game.
High variance games violate Scott Miller's "God concept" - even God (assuming he doesn't cheat) won't always win at poker.
My first instinct - because I usually dislike high-variance games - is to say, "Variance is bad." In fact, I used to think of variance as "slop" - mushy, chaotic randomness that got in the way of a game's true expression. (And I was pleased with myself, because that gave me a formal aesthetic with which I could argue that Tony Hawk 4 was a superior game to SSX3...albeit not as pretty.)
But this, as with all else, really is a matter of taste, and a matter of whether the variance fits the game.
Because there are good things about variance: in a low-variance game, once you've solved a challenge once, there's no reason to ever play it again. In a low-variance game, you can memorize patterns - and the game stops being about solving problems on the fly and starts being about memorization. High-variance can dump you in situations you aren't prepared for and get your adrenaline pumping. One of the exciting things about SSX3 is that your runs don't usually go as planned, and you make do with what you end up with. Spider-Man 2 is the same way - subtle differences in timing can mean you land on a completely different building than you intended to - now you have to make do with the hand you've been dealt.
In fact, one could argue that low-variance is boring, predictable, and that we should always strive for some variance because it adds replay value.
A good case in point is Mercenaries - (The good people at Pandemic are my new heroes, by the way, now that Ion Storm has bitten the dust. First Full Spectrum Warrior and then Mercenaries. Game design geniuses over there.) - Mercenaries is high variance. With one of the ace missions it took me a dozen tries or so to get to the first objective; then I died; and then it took me another dozen tries to get there again! Was I frustrated to be doing the same stuff over and over again? Yes, I was, but I probably would have been even more frustrated if that stuff was predictable, because it would mean however many minutes of being bored for each replay. Each time I played the situation shook down a different way, creating a varied gameplay experience.
What I need to do is pin down why the Ninja Gaiden and Devil May Cry boss fights bother me, but the SSX3 runs and Mercenaries missions do not. It's possibly in the kind of variance. With SSX3 and Mercenaries and poker the variance is more situational. SSX3: subtle differences in timing and action put you on a different part of the slope where different moves are going to be effective. Mercenaries: subtle differences in where the enemies go after you engage them creates different warzones. Poker: differences in the hands dealt create different landscapes to play in. The variance in Gaiden and DMC is usually just: which attack is the boss going to do next? (And is he going to be on camera when he does it or am I going to get blindsided?) My thoughts here are still murky, even to me. I'm certainly not suggesting that we take away the randomness of the boss attacks and replace them with patterns. Shudder.
One last note: high-variance games are easier to develop than low-variance ones. In particular, 3d videogames bring a lot of chaos with them that their 2d brethren didn't necessarily have, and tricks to make 3d less variant usually involve constraining the gameplay into two or one dimensions (the wall running of Prince of Persia, the rails of Tony Hawk, Jet Grind Radio, or Sly Cooper).