Wii vs Wii U is, as you noted, not relevant anymore. Same could be said about PS4 vs Wii U now, considering how huge the gap already is; same could be said for 3DS vs PSVita. Vita vs Wii U is the one I'm still missing, considering how similar their sales are.

What would interest myself would be some kind of analysis and evolution of long-term sales of several games/franchises which are noted for being leggy. I recon however that translating this into an article might me pretty difficult.

Digital sales would also be interesting - if there's a way to get that data.

The franchise sales comparisions you mentioned could get interesting. I just fear fanboyism can strike those hard if the franchises have not the same amount of games. Game vs Game duels could also become pretty interesting, just check Tbone's different Splatoon threads. But again, fanboy magnet.

A weekly list of games releasing for the different consoles, including digital only and Virtual Console

The PSP vs 3DS is a sales matchup I'd like to see.
How about having handhelds against consoles?
The PS4 is obviously killing it, but where does it stand compared to the DS. This is one I want to see because Sony is always talking about how the PS4 is the fastest selling PS console in their history and how the fans are raving about it catching the PS2. Unfortunately we don't have any weekly or monthly PS2 sales data in this site to go off of. So I thought of going with the next best thing, the Nintendo DS, which is just below the PS2 as the greatest selling system of all-time.
This way is so that we can see how much of a chance the PS4 has of topping the PS2, because if it can reach the DS, then it can reach the PS2.

Have you done any "Nintendo vs Sony" (handheld+home)

- All Hardware/games by year until now
- Curent gen hardware/total games by year..
- A comparision for 1. party titles also make sense

I have made a tread about it that will cover last 26 weeks of 2015.. But sudently we got alot of software numbers and and i choose to wait it out and finish it when we have all numbers for 2015.

Sales analyses showing the growth and/or decline of various franchises, development studios, publishers or individuals could be interesting. For example, you could chart things like the rise of Grand Theft Auto or the rise and fall of publishers like Midway and THQ or individuals like John Romero.

Yep. That's the main problem for a lot of the publishers. Either there'd be incomplete data because the companies are rather old (Midway, THQ, Virgin) or because the companies are too new and rely on untracked methods like iOS and Android (DeNA, GungHo, King) or downloadable distribution (Devolver Digital).

It could maybe be done with more of the 90s companies like Take-Two, or by just showing growth/decline over particular periods (like the entirety of the 00s or the generally-accepted console generations). It's food for thought anyway.

Hardware comarisons

GameCube vs WiiU
3DS vs PSP
3DS vs GBA

Software comparisons

Top 10 sellers per genre.
Top 10 selling franchises/gen.

I'd like to see a 3DS vs GBA gap chart, but I guess you'd have to do it one a quarterly basis using Nintendo's shipped numbers for that, because VGC doesn't have any numbers for the GBA besides the lifetime one.

PS1 vs. PS2 vs. PS3 vs. PS4 LTD if possible
same with Xbox vs. 360 vs. Xbone LTD.

I'd like Top 10 or 5 best selling games in X genre. Shooters, Adventure, indie, etc.

8th vs 6th Gen comparisons would be interesting

WiiU vs GameCube
PS4 vs PS2
Xbox One vs Xbox