First off yes, this is as objective as humanly possible. You can properly attribute influence, musical impact and cultural impact, and while the precise methods for doing so can be debated, the actual application of it to the proper artists, songs and albums is fairly simple to do.
The problem is, most people are so used to arguing music based solely on tastes that even in a debate like this that pushes for objectivity they still want to have their own subjective tastes used on the lists and their arguments boil down to just what you said - "because you prefer it" - and they'll manipulate the criteria to achieve that. It's human nature and has gone on since day one at DDD but that's also why the visitor's comments are not to be taken seriously, UNLESS (a big unless) they follow the specific criteria and as objectively as possible apply it to all of the artists in question.
Which brings us back to that. To start with, it's the Four Seasons, not the Four Tops, who are ten spots below the Who, and to confuse them might be an honest mistake, but I doubt the same mistake would've been made by saying The Guess Who rather than The Who. Secondly, lasting popularity is a way people who lose the commercial impact argument try and make up for it, but while that's not counted here (Commercial Impact is just that, chart hits and album hits), the Four Seasons are still just as popular as virtually any artist from that time frame. They have at least a dozen records in regular rotation on catalog radio, they had the hottest Broadway show based on their careers a few years back in "Jersey Boys" and their Greatest Hits Anthology on Amazon (a worldwide, non-demographic based mass media outlet) is ranked #165th in CD sales. By contrast The Who's best seller is ranked 1,342 overall. So even if you WERE to have lasting popularity included in the criteria, The Who lose that as well.
The Seasons influence is, or should be, obvious from the preponderance of the extreme use of the falsetto in 60's rock to their dense production and arranging to their songwriting and their musical impact at the time was extraordinarily high. The Who obviously have very strong credentials as well, but in the 60's they come up just short of the Four Seasons, even though when comparing both artist's ENTIRE career they'd win out easily. It wasn't the Who's fault the 60's came to an end just as they were in the midst of their peak stretch as artists, and therefore those years are split over two seperate decades lists, that's just the way it falls.
The criteria themselves are entirely subjective though. In other lists innovation is used as a criteria, Influence is described differently in different lists, in some it is about inspiring artists, in others it is about changing music. Some lists Popularity is given a low weighting, in others acclaim is counted in other lists it is not etc. etc.
If we used different criteria the list would be entirely different. It's not an objective list when the criteria is so subjective, there's no measurement that says cultural impact is a measurement of how great something is, that's just something that's been made up on this website. Cultural impact is no more an objective to personal favourites or nicest album cover being a criteria.
And yes, that's my point about objectivity, all this is is manipulation of the criteria and no influence, musical impact or cultural impact is not objective. The only way Influence could be objective would be, say, to ask every act who ever existed who they were influenced by and there somehow to be some standard measurement of how influenced they were by them (which is impossible). Fact is, music that everyone knows about takes up about 0.001% of the total music that's made and all opinions on influence or musical impact for example are based on just famous musicians, not every musician ever. Everyone's opinions is solely based on what they read, I don't think people will manipulate them directly, but their sources certainly do.
Sampson - Firstly, you have to remember I am not American, so they may well get played constantly and remain as popular as say, The Who, in that case you may be right and you're right I got the mixed up because I'm really not familiar with their music, because they are not in my interest zone, but neither are the Who, who I've known about since the age of about 4 and have regularly heard their songs on the radio,on tv and in the media growing up, because they are far more engrained into popular culture, at least in my country.
Amazon sales are based on one week's sales, so I'm not sure how one week's sales point to lasting popularity. And amazon.com isn't a worldwide organisation. Those sales are based on amazon.com sales, which operates in the USA solely. Other countries have their own versions of amazon, which have completely different charts. The same Greatest hits album is ranked at #50,098 on amazon.co.uk for example.
And no, I do not know much about vocal styles or production, so no it's not obvious to me that the forwarded the use of the falsetto in rock music or the dense production to me as I do not know if any artists before that had used falsetto or produced records in such a way before.
Again, going back to the subjectivity thing, what are we basing their musical impact at the time being extremely high? The words of a few individuals? Certain popular musicians? What? To me that it the criteria that is so easy to manipulate when it's so loosley based on what other musicians thought of it at the time.