A spreadsheet works for fifty games. By a few hundred, you want something that knows which games exist on each console. Here is a method that scales.
Pick the shelf you know best. Finishing one console gives you a quick win and shows you how much effort the rest will take.
For each game, note the title, the console, and the condition: loose (cartridge or disc only), boxed, complete in box, or sealed. Regional versions and special editions are different items, so write down which one you have.
Ticking games off a full list of everything released for a console is faster than typing titles, and it shows what you are missing. That is how Chamberla Collector works: you check off what you own and it shows percent complete per console.
Decide up front whether you count digital copies. Most collectors track physical only, because that is what sits on the shelf.
Scanning the barcode or the label confirms a game is really in your hands. See how to verify a game you own.