Compared to your other covers man, this lacks something desired.
I think you could play around with shading, because poor old Mario looks like he has been drawn and quartered.
Saying that, these are your custom covers, and if you like them, then it doesn't matter what anyone else thinks man.
It would definitely be a surprise if you did go with these covers, as your past work has been based around white spines and banners.
It's up to you bro!
What do you mean by shading?
Well, I have black SNES spines, white SFC, white n64, white GB/GBC/GBA, white Wonderswan, dark warm gray Neo Geo Pocket, red Genesis, and black TG-16. So not
everything is white.
I say you should add some sort of symbol on the spine like the SNES and N64 covers, I do like what is there, but I feel there should be more relating to the game, the back seems to blank.
Are all the covers going to be red? it does work for NES, but maybe a black to blue gradient with stars or something like what was used on the NES box with a red stripe on the top or bottom. or maybe something like the Black Box games.

They won't all be red. Each will have a sort of "theme color". SMB 2 will be light blue, SMB 3 will be yellow, Zeldas will be gold, and so on. Since these are so minimal, it will be more about color choice than anything to differentiate between titles.
The back seems blank because it IS blank LOL! The way I'm looking at is that NES games are (for the most part) very simple. Also, I have a TON of games to case, NES, SNES, Genesis, and otherwise and not a whole lot of free time at this point. It's ALWAYS been my plan to go super minimal with the NES covers, and now more than ever I sort of
need to.
My goals for NES covers are:
• Clean, simple graphic representation
• Easy to produce
• Retro look with muted colors
• Easy to read on shelves, more like books on a shelf than games, hence the paper texture overlay and book-like spine treatment (i.e. publisher and title only)
Like I said, I am NOT going to make these any more complex than this. The only other thing that isn't visible on the mario cover are graphics for Zapper and power pad compatibility (right next to the player icon). I thought about addding copyright/trademark info in the lower bar on the back, but it just seemed like too much for what I'm going for. Let me change that around and post a preview to see if any of those things make a difference. The only other thing I had considered was a publisher/developer logo on the bottom of the spine, but again, made it seem sort of cluttered IMO.