I use IGN for the following reasons.
1. I love all the column options. Box art, developer, publisher, release date, genre and especially the reader ratings which I think are pretty accurate!
2. I like the stats. Favored developer, collection value(even though its way off), the average scores ect...just wish there were more!
3. I like how they have pretty much a complete database.
4. I like all the different ways you can sort and customize your collection and how easy it is to do.
5. I like how the wish list has all of the same features the collection does.
The only things I wish they had were a place to add pictures and a column that shows how many other users in their database own and want a particular game(like Gamespot does).