You're right. Opening Box Office numbers do matter. EA stock took a dive because the numbers were down 40% its opening week vs. Madden NFL 13. Stock holders DO take notice of that sort of thing hence why the debate is relevant.
To be fair, there are possible explanations as to why the open sales dropped compared to the year before. Like introducing a new console to the franchise, but that's just a soft theory. All theories will be soft until we see how it goes for Madden NFL 15.
Still, it's good to debate because despite the reasons, the stats are fairly accurate. I think it's still odd that an anniversary game didn't break last year's record. That's just me though. I understand the next-gen argument, I just don't think that's why Madden NFL 25 didn't do as well as Madden NFL 13.