For those who are only getting their Opening/Ending fix via Youtube, may I suggest visiting
https://openings.moe to get your high quality video fix.
While I'm on the subject of streaming quality, I've seen some unfortunately low-quality videos of
Record of the Lodsoss War TV linked in here. For shame. You can look here for a higher quality video:
https://drive.google.com/file/d/0B1Ea2q-kqmL_NkVBSl9qNzRrTzg/view
Now, on to the main event - opening credits. There's a long history of excellent title credits in anime dating back many decades, which means that it's quite difficult to list anything like the 'best' credits around. Many opening sequences have cool music, or do a great job setting up the tone of the series, or make you 'hype' - so what makes an opening "one of the best", beyond simply personal preference? It's very hard to say, but certain sequences are so iconic that they influence dozes of others. Other opening are extremely original in their visual message, or execute on an idea in very effective way.
Here's my list, in no particular order:
Ping Pong
Mob Psycho 100
Re: Cutie Honey
Garo Divine Flame
Kyousougiga TV
Zan Sayonara Zetsubou Sensei
Tiger Mask
Record of the Lodoss War TV-
Neon Genesis Evangelion
Kiznaiver
Cowboy Bebop
Dirty Pair
Dirty Pair Project Eden
Gunsmith Cats
City Hunter (OP 2)
Kimagurae Orange Road (OP3)
Baccano!
Death Parade
Sailor Moon (OP 2)
Blood+ (OP3)
Gundam 08th MS Team
Maria Holic
Arakawa Under the Bridge
Space Adventure Cobra
FMA Brotherhood (OP1)
Pyscho Pass (Opening 2)
Nadia: Secret of Blue Water
Subete ga F ni Naru:The Perfect Insider
Concrete Revolutio - The Last Song
Michiko to Hatchin
Paranoia Agent
Welcome to the NHK
Gatchaman Crowds
Serial Experiments Lain
Nichijou