Retro Rewind (blog/zine): [Link]
I've been at this awhile. I play anything that looks entertaining and I am sucker for pixels, roguelikes, and atmospheric games and tend to steer more towards older stuff--especially for systems I grew up with (there were a few...). I also really enjoy repros and homebrews.
My collection is pretty straight-forward. Just a few notes, though. I use collections to keep track of certain subcategories within a system (ie. WiiWare, PS Minis, PS Classics, etc.) to keep the system list more down to size and make it easier for me to see what I've got where. Some things aren't separated because I didn't have this idea when I started.
Homebrews, Repros/Hacks, and other such ephemera are lumped together in appropriate collections that appear at the top of a system's list. I also keep track of all DLC so I know what crap came with the game. If I play with Mods, they will also be listed with the DLC.
Lastly, I use the Miscellaneous category to catch things I don't want intermingled within the main system categories, or for things I feel fall outside--or don't exist--a category. MMOs, BBS Door Games, and things I'm constantly playing and just don't want lingering on my Now Playing List because sessions are few-and-far-between all end up there.
I have played a lot in my lifetime, so I'm not likely to delete things I no longer own.--finished or not. I want to avoid rebuying stuff I dropped (which is a thing) as well as avoid so many duplicates across systems (unless I really mean to).