It sure could. Then do it by units sold. More people (whatever their tastes) enjoy certain types of games more.
I sincerely doubt that Dominions sells on a Civilization scale. That doesn't mean it's an inferior game in any way shape or form. But that the tastes of consumers dictate how they purchase games.
Just like how some people for their TBS goodness prefer EU2 or other severely complicated games that I may not enjoy as much. I wouldn't say either way Dominions or EU2 is a better game than the other, only that one game caters to one specific subgenre of TBS and the other caters to what I enjoy in a TBS.
This is more of an industry thing I think instead of a consumer thing. A good read on this would be the Shrapnel Blog about niche games and general vs hard-core stragtegy from their perspective instead of the straight consumer end find it
here