I add to my colection here all the consoles and always try to add all the accessories that I feel relevant. For example, I won't add a loose SNES controller, a third white DreamCast or a PC Engine AV cable here, but if I buy an SNES Capcom Pad Soldier, a white Sega Saturn or a PC Engine multitap for example, I'll definitely catalogue it here.
And if I purchase some doubles, I usually add them to my Sell List.
I use the VGCollect as a means to keep track of what games/systems/accessories I already have and what is their current condition. This way, I won't waist time looking for something that I already have at the same time that I can check if I already own the manual or box for some item when I'm out in the wild.
I never add any digital games though.
I don't feel like I really own the game if I cannot touch it and I'm always searching for physical copies of the games that I purchased digitally.