While I think every 3DS game is a bit overkill, I completely understand where OP is coming from. My 3DS has every ROM from NES, SNES, GB, GBC, GBA, Genesis, Wonderswan, NGP, and more. I have a 64gb MicroSD card and all of those ROMs only take up a few GBs. There's something to be said about being able to play any game that has come out on those systems at any moment. I actually spend a lot of my daily commute trying random games for random systems just to see what crazy stuff was made 20 years ago.
But ya, every 3DS game would take up an unbelievable amount of room. Though, I bet everyone in this thread would love a 3DS loaded up with every game ever