Clean everything up. Take off all the unnecessary labels or stickers. Do retrobright on any yellowing plastic, like Snes for example. If console/cartridge too dirty, open it up, air in can, isopropyl alc, resolder any loose points, add solder where is not enough.
Now I never replace or restore the actual game labels or any damaged art. That I keep for historic value. Also, I rarely replace the cases or boxes if I have any. I dont need those to look new.
Old but very clean is fine by me.