Stopped reading at "you fans were in lala land because to you thought dmc4 was just perfect" Nope, I didn't and I don't know many that do. It was good, definitley could've been better but it brought up a lot of questions. It sold 2.7 million copies, which according to this chart is more than any DMC had sold before.
DMC 4 was a trash game. I played the heck out of DMC 3, I knew how the mechanics of the game worked, and I beat the game on DMD mode. That being said, I'm shocked the OP's friend who played the whole series never heard of jump canceling. I'm guessing your friend just beat the games on normal mode, because you need to know the mechanics very well at the toughest difficulties.
When it shows DMC 3, is it including the Special Edition? How do the sales of the fifth anniversary boxset figure in?
Nope. Something else to note is that charts from 2008. I did some further research and found stats from 2012. DMC1- 2.99 Million DMC2- 1.97 Million DMC3- 2.09 Million DMC3 SE- 2.21 Million DMC4(Both Platforms)- 3.42 Million DMC HD- 550,000
Remember these are all worldwide. No stats on the fifth anniversary boxset though. In total the series has sold 12.54 Million games. I'm sort of confused about DMC4 though because that's a pretty big boost from the 2.7 million Capcom complained about when they just announced the reboot.