I got directed here from Atariage 3 years ago when I was struggling to find a good replacement for my old IGN list. They'd changed their setup to not even allow you to sort by system or alphabetically- just by 'date added'. It didn't work for my large collection at all. Anything else I'd tried either didn't support my full collection, had terrible sorting that made it hard to parse my collection, or had a lengthy approval process for adding new items (assuming it was still being moderated at all.)
This site literally gave me everything I was looking for- a diverse database with support for every system I owned, intended to own, even things I'd never heard of. The ability to immediately make new listings for items not in the database (I know some people would prefer moderating new listings, but personally, I hate having to wait to see if/when my titles get added). An active moderation group keeping the database maintained. And, just for fun, a few basic statistics of your overall collection to look at. I remember being stunned at the level of accuracy/detail in the listings when I was entering my NES collection & found listings specifying 3 or 5 screw carts. I didn't even know about that at the time!
Having been here awhile, the only thing I'd really like is, when looking at one's collection breakdown, to be able to click on each category & see what's in it. What accessories do I have listed? What demos? I know I can access that on a system-by-system basis in the sidebar, but a quick overview would be great. Otherwise, I don't think I'd change a thing. I spent years looking for a site just like this, and I'm damn happy I found it.