Okay, here's my top 10 list (in no particular order); it may be different than others for sure - I'm a fan of Japanese wrestling have seen some these live in person over there. I'm making it based on my own favourite themes of all time, based on the way it fit the character, the consistency it delivered, and the importance of its presence in establishing the anticipation and atmosphere.
1. Shinsuke Nakamura - Subconcious
Just iconic in Japan. This theme defined the King of Strong Style in the 2010's. Hearing this live at Wrestle Kingdom 10 as he walked to face AJ was ridiculous.
2. Kenta Kobashi - Grand Sword
A goddamn wrestling god in his own right, the chants of 'KO-BA-SHI' as he makes his way to the ring are must-watch vids on YouTube.
3. KENTA - Art & Life
KENTA / Hideo Itami's theme in NOAH slapped like no other theme at the time, this guy was legit dangerous and this music oddly fitted him too.
4. The Four Horsemen
A passive guitar riff with no lyrics makes this one arrogantly great, which is what the Horsemen were.
5. Rob Van Dam - Walk
Fans chanted along with this awesome Pantera song. Fit Van Dam perfectly, too.
6. AJ Styles - Styles Clash
AJ's Bullet Club theme is 2015/2016 was just f'ing sick.
7. Kenny Omega - Battle Cry
It's new, but I love it and fits Kenny's persona so well.
8. The Great Muta - Trans Magic
Can't make a list like this without my boy Muta's greatest theme ever.
EDIT: Ozy_Flame reminded me of this one. This is my fave Muta theme ever.
9. Legion of Doom - What a Rush
What kid didn't think this was one of the greatest songs ever? LOD was sick as #### in the early 90's.
10. Jake Roberts - Trust Me
Dark and cerebral. Totally ahead of his time.
Other amazing themes I love:
Great Muta - Great Muta Concerto
Hulk Hogan - Real American
Stone Cold Steve Austin
Mistuharu Misawa - Spartan X
Minoru Suzuki - Kaze Ni Nare
Kazuchika Okada - Rainmaker
Silas Young - United Divided / Voodoo Johnson
Kevin Steen - Unsettling Differences / Blue Smock Nancy
Sandman - Enter Sandman
Jushin Liger - Ikari No Jyushin
Jushin Liger - NXT Brooklyn (2015)
Christian - Take Cover (TNA)
Christian - Just Close Your Eyes
Dan Severn - Fighter
Pete Dunne - Bruiserweight
AJ Styles - Demi-Gods (ROH)
.... K, I'm done.