Hmmm, storage is really a personal thing so it depends on the aesthetic you want to end up at the end too. Saving space wise, are we talking getting rid of the cases @Spacedeck ? If so, I think you start off with the hard case storage options like below off Amazon. Stores 96 DVDs/CDs and you can choose nice vibrant colours to separate perhaps games from different consoles, etc.
CD Hard Case - Multiple Colours at £11.99 from Amazon
If you have something like this then its just finding some nice cabinets to either show them off or not as the case may be. Do you want to show you have them or is just storing them the main thing? The manuals could follow a similar design if you want with this colourful file organiser. Would easily fit a ton of manual in it.
File Organiser at £11.92 from Amazon
Personally, I think you could go for a mix and match approach if most have to be in storage due to space, I think a cool feature is to have 'featured games' out on display. On Etsy, you can find people making multiple designs where it will hold a cartridge or game on show and this could be something that you can interchange over time. Personally this is why i keep game cases and I'm looking into making bespoke ones for games that I don't keep the cardboard boxes for (Gameboy, Game Gear, N64, etc), although they need more space which may not help you in this regard. An example is below (there's more from the UK with cheaper delivery)
Cdmount™ CD License Plate and 8 Track Wall Frame Display & - Etsy UK
WWW.ETSY.COM
This Display Cases & Cabinets item by CollectorMount has 1077 favorites from Etsy shoppers. Ships from United States. Listed on 31 Aug, 2022
Pictures of each below:
Gives us more details on what matters to you and maybe we can bounce some ideas around that's nearer to your interests.