Hopefully the brackets I've used are meaningful - if not, well, never mind. I'm firmly in '<25', which is unsurprising considering I'm only casually into the genre, but I was still quite shocked by the breadth of experience ideally expected of voters. I'm interested in responses from non-voters as well as voters, obviously.So what constitutes "widely and deeply experienced"? That's impossible to truly quantify, but as a general guideline: voters should be familiar with nearly all (95+%) of the games on previous years' top 25 lists. Furthermore, they should be equally familiar with nearly as many (90+%) of the shmups on previous years' honorable mention lists. And, to the extent that other games voters have listed are available, would-be voters should be familiar with 50%-65+% of those games, as well.
And what constitutes "familiar"? Basically, having played it enough to understand the gameplay mechanisms that make it unique, and/or fun and/or historically important and/or any number of other things you might take as helping define "top."
Part of the issue is probably the somewhat vague definition of 'familiar'. I'd hesitate to claim familiarity with anything I've not at least cleared (ignoring loops), but some allowance has to be made for games one simply doesn't like - how long do you need to've played something with mechanics that make you want to throw pointy objects at the designers before dismissing it? At the opposite extreme, how well should you remember something you know you once played to death? There's some easy Gradius-eque game that's the only shooter of it's sort I ever learned to the extent I was one-lifing consistently and wound up looking for ways to make it spawn extra 1ups for points to squeeze a last bit of longevity out of it. I certainly knew that backwards at some point, but don't even remember what it was called any more.
Anyhow, there's a lot of room for interpretation here, and it's obviously quite relevant - I just wanted to note I'm interested in how many games people consider themselves qualified on according to their own interpretation, not someone else's standards. People's take on the familiarity question would be interesting, but hopefully we can refrain from e-peen confrontation about it.
