Of course.

Though when Call of Duty sells over 20 Million units per version every Year, then that is one huge target audience that keeps jumping back into the franchise and people are quite clearly happy with the games.

A bad game wont sell over 20 Million units every Year.

Macdonalds has bad food and yet people come back to that as well. People just buy what they're familiar with. 

The first two were a revolution in FPS games; perhaps even gaming in general when it came to pacing and stress and the storytelling was sublime and very direct. The two first games are by far my favorites in the series, followed by Modern Warfare, which was nothing short of fantastic. Then it all went downhill.

Define "bad".

The point is it does the job its supposed to do, better than any other game on the market. Thats why it sells more than any other videogame, every Year (aside from GTA5 that is).

Games cater to different demographics. Some games cater to the simple minded masses. It's those games I find bad. And yes, that's not a fact, but my opinion.

don't even think i've ever played a COD,maybe an early one but you can't argue with big numbers,that is the casual effect in place right there

most people aren't geeks like us hanging around vgc they just have time for a few games a year.COD being one of them by the looks of it

Are you saying that only simple minded people enjoy CoD?

Best video game franchise??? It's an ongoing yearly same game that never stop from 6th through 8th generation!

What about Pokemon??

Impressive. What is the best selling series ever?

It's not funny at all. It's actually true! And it's a very good argument to support the sales = quality theory. A game can't be bad if it sells so well. A couple of people can be wrong but, 20 million? That's impossible. Therefore we can't state that COD is "bad".

In fact  let's use Wikipedia for this one: "Simply put, a quality item (an item that has quality) has the ability to perform satisfactorily in service and is suitable for its intended purpose". COD proves this every year, so we can assume that it's a quality product. In fact we can assume it's high quality because it proves itself every year with those monster sales!

COD is a high quality videogame franchise, so it's only natural that we call it one of the greatest videogame franchises! (THE Greatest videogame franchise is debatable)