Your anime list is missing out a lot of good titles with amazing openings. Serial Experiments Lain, Psycho-Pass, Monogatari Series and a lot more. I seen you've watched more Gintama, so you should have seen one of my favorite openings from Gintama. The 3rd opening is my favorite in the original Gintama. Nothing beats Sakura Mitsutsuki though, the 3rd opening in the last Gintama TV series so far but you're pretty far so I doubt it's on the list. PM and I'll give it a listen.