Just to throw a thought in here WRT to the issue of sales.
Allow me to posit just for a moment that the "most excellent" or "best quality" (or whatever buzzword you like to use) gaming material can be defined simply... "that which has the greatest impact on the hobby of role-playing in general."
Think about that one for a minute before responding... it stands to reason, at least in my mind, that role-playing games do not exist in a vacuum. You cannot say that a particular system is empirically better or worse than another system. You might say that it is better for recreating verisimilitude, or that it is better to learn because the rules are clear, or it is better at defining fantasy/future/your choice of whatever. But people use role-playing systems for a variety of different things... and no system is optimized for all things, because one of the trade-offs you constantly have to make is "simplicity versus realism." You can't have something be exceptionally realistic AND exceptionally simple at the same time.
Furthermore, you can't really judge the impact of a role-playing game in a vacuum. You have to see how it works with your gaming group, with your friends. On a larger level, you have to see how it works with ALL gaming groups. The "best" games, at some level, are the ones that impact a large cross-section of gaming groups, because these are the ones that do the most to aid the role-playing experience across the entire set of role-players.
Sometimes, that influence is felt directly. If a million people pick up a system and start playing it, that system clearly has an impact on the RPG world at large. This is "Sales." High sales are not a sure indicator that a game is the "Best" game out there, but in general, sales are a good indicator that a game is not the "Worst" out there. To return to the example of "Titanic," was it the best movie of all time? No. Was it a horrible movie? Probably not. The same can be said of all the movies on the top-50 grossing movies (preferably adjusted for inflation) - only one can be the "best," but surely almost all were at least "good" movies, no?
Sometimes, however, the influence of a game is felt indirectly. It has a small release or a cult following... however, pieces and ideas from it are seen and picked up on by others, and eventually it impacts things "down the road" a few years. The original might have suffered from poor writing, poor editing, poor production values, etc., but eventually someone comes along, sees the potential, and re-uses/re-works it and we see the impact "ripple" through the RPG industry at a later time. D&D was not the first system to come up with "Skill Points" or "Open-Ended attribute scores," but it has since incorporated them... the place where they were first developed and put into the collective RPG consciousness, then, was a quality game (sadly, I don't know where these first germinated).
Indirect game influence is rarely seen directly, because it takes so doggone long. Industry professionals, however, are in a better position to see the potential and judge where the "indirect influences" are likely to come from... because they are the ones who will likely take those influences, meld them into their own products, and eventually mix them into the mainstream of RPG culture.
Thus, both sales and "industry nominations" are important factors, IMO. Sales is a good way of at least saying, "these products are good."
The Sigil's Theory of Quality*:
High sales volumes for an RPG product are a good indicator of high quality.
*Quality being defined as the impact the ideas in an RPG have on the hobby as a whole
Note that the reverse is NOT necessarily true... it does
not follow from the above that low sales volumes for an RPG product are a good indicator of low quality.
Obviously, it's pretty easy to use "sales figures" to at least get a handle on what SOME of the good product is... but it doesn't mean that will find ALL the good products. Sales figures, however, serve as a useful "starting point." You can at least look at some of the top-selling products and figure that those products are impacting the hobby as a whole. It's the work finding the "high-quality, low-selling" products that a nominations board needs to be for.
I would suggest that neither "sales" nor a "nominations board" obviates the need for the other. Perhaps you take the "top 5 sellers" in a category and the board nominates two of those plus any 3 other products or some such. But at the very least, throwing sales into the mix helps eliminate the need for the nominations board to read every product that crosses their desk.
Hope that's coherent, but I think my "Theory of Quality" with the note that the converse is NOT necessarily true is my main point here. If something sells a lot, it WILL impact the hobby for good or ill, and that means that it WILL influence the games of a lot of people... and that means that it IS an important product.
--The Sigil
