"Realistically" isn't a fair question. Clearly the mere mortals cannot compete with the metas/supers/amazons/etc. Not even Batman. If, though you were to take away most of the bullshit stuff like Speed Force abuse (and the fact that Ares is a fucking god, and Grundy is a zombie, literally), it may be a bit more clear. More than happy to keep everyone's abilities, of course but let's give the mortals the krypto-pills so they can stand on a more even footing.
It's hard to judge due to all the superpowers floating around, but in fighting ability?
1. Diana. She is, in Batman's words, the JLA's greatest melee fighter. Only above the boys in #2 due to Batman's word.
2. Arthur/Ares/Lobo- these are the big boys. The warriors.
3. Clark/Doomsday/Billy/Adam/J'onn/Barry - where things start to get a bit weird. These guys could muscle their way through pretty much any situation, or for Clark/Barry/J'onn, break the rules entirely.
4. Hal/John/Sinestro/Zod - Lanterns can never be discounted, and Zod is Superman-lite thanks to minimal yellow sun exposure.
5. Bruce/Grundy/Deathstroke/Bane/Dick/Ollie/Joker/Hawkgirl - Bruce of course, is one of the greatest human hand-to-hand opponents there is. Dick is faster than Bruce, by a hair, according to Catwoman. Damian doesn't exist, IMO. Deathstroke has beaten Bruce, Bane broke his back. Ollie levelled himself up after taking two to the chest from Shado, and trained under the same masters that taught Deathstroke. He subsequently fought Deathstroke on pretty much even footing at one point. Were physical abilities being equal, Ollie is more than able to handle himself. He trains with Canary, too. Joker, because Joker. Shayera is Thanagarian. 'nuff said.
6. Babs/Cyborg/Selina/Harley - where human abilities start to waver and we get to the people who rely more on their abilities or technology only. Babs is entirely capable of handling herself, even when paraplegic. Selina is along the same lines. Don't count her out, but face it, she's no warrior. Vic is readily capable, but nowhere near the fighting skills of even Dick or Ollie. Harley is unpredictable as ever.
7. Zee/Raven/Lex/Frost - Zatanna has barely a rudimentary knowledge of hand-to-hand, much like Raven. Lex is more likely to outsmart you and make you defeat yourself. Frost..I have no idea, she's relatively throw-away.
I mean, go ahead and tear this apart - there's so much to play with.
