I'm not too worried about RE7. For the record Resident Evil 4 is VERY similar to RE7, it under-performed at the time frame too, RE4 was under development for nearly five years and during the same time frame it managed to sell less than a million copies, and this was after REmake, Zero, and Outbreak had all under-performed as well. Resident Evil 4 sold less than a million copies on Gamecube in the first half a year, the PS2 port moved things along but RE4 still undersold on both during the first year. Resident Evil 4's sales became better by the waiting game, reputation, and various ports. The Wii version went on to sell a lot, as has the 360/PS3 ports, the PC Ultimate HD Edition, longer tails on older systems (the gamecube and PS2 versions kept selling for a good number of years after release). Resident Evil 4 wasn't an initial success but it went on to have a good tail life a little over a year after it had released.
I think RE7 is slated for the same fate, people seem to forget this year has been packed in releases so the slow sales growth currently doesn't surprise me because there's still a lot of shit releasing right now that I think most have to be very selective in what they pick up. That and Resident Evil 7 is still in the phase where people still have prejustices, look in the sales topic and you'll still see people think it's a hide'n'sneak horror game where you can't defend yourself, about it which will clear with time.
Plus with all of this Resident Evil 7 still hasn't had its bigger content rebound yet which is sure to attract both some new attention and sales, as Not A Hero has been delayed until much later and the last DL is still out there, and Capcom have been mostly silent on both of them recently the 'resurgence' of RE7 in media is on the backburner since February in a busy year, but as RE7 was well-received and many liked it in the critical realm they will certainly cover Resident Evil 7's DLC when it comes around.
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This is a completely different topic not directly linked to RE7, but I'm curious what I can do to help the horror genre as a big horror enthusiast. I think one issue horror games have right now is there's a lot of people who aren't interested in them due to lack of exposure to the genre. This issue will solve itself I think, but let me explain. I think right now horror games are in a second golden age, and they're doing fine but not great either. A big part of this I think is that there was a GIANT lull of horror games for a good half a decade at least, a lot of horror fans you'll find grew up with horror because it's harder to convince adults to try something new and many people have concluded they don't like horror when an adult when more often it's just they got scared as a kid and convinced they hate it now, I went through the same thing and I see a lot of people like this. And I think we're in a period where many of these people didn't grow up with horror games and lack that exposure so most horror fans are in two groups; the old and new wave. You'll notice when talking about horror games most people will talk about older games and a few of the very few newer games which jump at the forefront due to lack of exposure and coverage from gaming media in general, there's a whole second wave of horror games happening right now with several horror game gems released every month essentially, but so many in the gaming mainstream are out of the loop of the genre it's almost saddening.
But I think this problem will solve itself in the next few years, horror games got a LOT of exposure from the YouTube era and the rise of Let's Plays, and many people who are growing up now grew up with all sorts of horror games that were popular with teens as almost every big Let's Player was a horror game let's player in some capacity. So I think while right now there's a sort of 'lull' in new horror fans and exposure there's probably a fairly large audience of people who grew up watching horror games who a portion of those may get more into the genre and playing it themselves in the next few years. Horror currently has a problem due to so few people willing to give the genre a chance honestly due to presumptions they have about it, but I think with a wave of people who grew up with a lot of horror games the scene will change drastically in the next few years.
Resident Evil 7 was a hit with these audiences, so I think it getting re-releases down the line will give it much growth in a similar way as RE4.
Also while RE4 didn't sell great initially, it sold much more down the line, and then Resident Evil 5 benefited a LOT from the good word of mouth and extended sales of RE4. To some extent I imagine RE8 may benefit from this in a similar way as well, and I'm pretty sure Capcom knows that. If you watch how RE games have done, it's almost always the entry after a great success that benefits it. IE, RE2 after RE1, RE5 after RE4, and in its own way you could say RE6 after RE5 (RE6 underperformed but I think a lot of its sales were pushed by co-op and fans of RE5, which was well received and a good game even if not what everyone wanted). Resident Evil 7's sales aren't bad, they might not be up to expectations but they certainly aren't bad, and the positive critical reception and word of mouth I think will help in the long run, and I think RE8 will benefit from RE7 being a good game to many because more will be more positive on RE8 than RE7 pre-release, and say what you will but pre-release coverage does do a lot for a games sales especially in a busy year of releases.