I've always felt that in terms of just pure cosmetics, the Gears of War franchise has been king. It's carried through to Gears 5 as well. While I've personally never really felt cosmetic items were of the utmost importance in any game at all, the GoW series has basically made it limitless...they've even got weapon and armor skins that aren't just static, but with things like fire and electricity flowing around you, etc. Super cool.
