Colecovision is missing from the drop down list. 

I would be happy if I could track my Gizmondo games.

Sure they are low in numbers, but if the N-Gage and Pokémon Mini gets one, Gizmondo should get one too! 
 

Many collector's editions of games include a steelbook case as a limited or exclusive item that is heavily traded and sold in the aftermarket on eBay and personal ads. I believe many of them have a significant value that can add another layer to the item checkboxes for included items (such as box only, manual only, loose items, etc). It could also be included in a separate section like the Figures tab as well. I have many of these cases myself and would love to be able to have prices tracked for them and have a way to keep an updated list of the ones in my collection. Thanks for your consideration! :)

Brazil was a huge market for SEGA. The Master System and the Mega Drive were insanelly popular back in the 90s. So they got some exclusive games and this also includes some games for the SEGA CD. I believe its a mistake to ignore the game library of this south american country.

Would be cool to be able to put the price you sold an item in your collection for. This would maybe mark the item as sold for your own purposes. Would be nice to also have a running tally for how much money you have made on all items sold. I have been adding comments to my items that sold and marking them as non working to reduce the value to $0

I like too see what i own and all that other stuff but not everthing is here for example i have a PAL Playstation 4 slim Gran-Turismo but it isn`t shown. So, it would be nice.

Users can add eBay Listings and then they would be put under the corresponding catergory (Loose, CIB, New, Box or Manual).

I like there to be an option to remove all the the console's in the filter list that do not have a game in your collection. That way I don't have to scroll though as many options and I can get to what I want to see quicker