I like using http://www.vgcollect.com. It already has a huge database and you can add games that are not already in it, it has separate collection, wishlist, selling, backlog and currently playing pages. I can write in notes and other details like when purchased, cost, and a checklist for cart, box manual, and other inserts each each title, and I like the interface. Once you do add your lists on there, you can export it into Excel. It also has a decent mobile version.
Here's a sample page (not mine): https://www.vgcollect.com/scott