Yes and no. Generally, a high quality film or game will generate above average sales if it is marketed properly. Some of my favorite games are very popular (WoW, Myst, Sims, Warcraft 3, Diablo 2, BF 1942, Baldur's Gate, Dungeon Siege, Half-life etc, etc.). Those games sell a lot of copies because they are, in my opinion, very good games. They either introduced something new or did something old very well. Sure, none of the games in that short list are my absolute favorites of all time or anything (Baldur's Gate is close), but that's not because they are bad...that is because I have an eclectic taste in entertainment.
As for films, well, there are WAY too many movies out there to begin with. Marketing is what makes most movies popular simply because it is the only way to stand out in the pack. At any given point there are 15-20 different new releases out in theatres. Games are a little easier as, excluding the indie games that have gained in popularity lately, there might only be 15-20 new releases over the span of a month or more and 5 of those will be garbage like Barbie's New Dildo or some shit.
Basically, the majority of people on this site are nerds and it isn't cool in the world of nerds to like the "mainstream" things. Once something gets too popular, nerds shun it.
P.S. I don't mean to use the word nerd in a derogatory way.