I think it's worth pointing out that most of the public-facing verbiage indicates (to me, anyway) that questions must be answerable, not that they must only have one correct answer and that you must accept that answer. This implies to me that lists are acceptable, even if the question's original wording doesn't conform to the precise SO "standard." Comments, editing, and education are going to be just as important as the guidelines we establish here. And if the asker thinks a specific response answers their question and they accept it, even better.
It's also important that we try to understand our audience. The Area 51 proposal defines our audience as "passionate gamers from all platforms (computers and consoles)." Yes, at first, our users will be a subset of the SE family of sites. Many of them have technical backgrounds and can be reasonably expected to know and follow the rules (myself excepted, eh? ;]).
But if/when the site exits beta and gains popularity, can the typical gamer--even a passionate one--really be expected to read up and scour existing questions and comb meta for an hour just so they know what kinds of questions they can ask and how to ask them? The FAQ goes into some detail, of course. But (and this is written with my gamer, non-tech husband's input) if I'm a typical gamer, and I have a question, and I find a gaming Q&A site, I'm likely to just head straight for the ask page and get really ticked off when my question gets closed because five strangers didn't like my wording or that I asked for a list.
SU is probably the best corollary we have for this type of behavior, but I'm not active over there and don't know how it was handled.
Something else we need to consider is whether passionate gamers will end up equaling passionate, returning forum members. If that means allowing a broader range of subjective and open-ended questions than would be typical on other SE sites, I don't think that's a bad thing. Individual SE sites are going to be run by their individual communities, so I don't think we have to stick strictly to the SO standards of what is and is not an acceptable question.