thor vs superman would be a very close fight, but I think thor would barely win due to superman's weakness to magic
hulk vs martian manhunter would be good too but i think manhunter will eventually win that with his shape/density shifting powers
i'm not so sure about GL vs iron man, this fight could go either way. GL could trap iron man in a green bubble then make it compress until iron man becomes a little metal ball or iron man take down GL with a good unibeam.
Wonderwoman vs antman I think ww would win because he wouldn't be the first giant she's faced, but antman might win if he summons a huge ass ant army. But if this fight is limited to fists, I'd have to give it to ww.
hawkgirl vs black panther: both rely equally on high tech weaponry and skills to take down their opponents. Hawkgirl is stronger physically but I'd have to give it to black panther due to his superior skills and versitality.
flash vs hawkeye the loudmouths of each team who achieve great feats once in a while but seem pretty useless for most of their series. Flash blitzes hawkeye. no contest.
Batman vs cap : the two peak humans who have great brains and resources but prefer to rely on a more traditional fighting style with traditional weapons. I'd say they're dead even and one would only gain advantage over the other with a lucky shot like what happened in the jl vs avengers crossover
I think people here really underrated batman and cap. I don't know if it seemed like this to me, but they seem to have been able to accomplish feats that shouldn't have been possible for even peak humans.
for example, in "fury", batman single-handedly managed to take down a team consisting of Star Sapphire (basically a green lantern but in a different color), Shade, Copperhead, Solomon Grundy(who was able to go toe-to-toe with superman), and Tsukuri(random ninja).
Also, in the last episode, he even managed to faze darkseid with a batkick then dodge his omega beams.
Meanwhile, cap was able to beat a team of superskrulls when he was trapped on a skrull ship and was able land a pretty decent hit on hulk.
I didn't add wasp here because I think we can all agree that she's borderline useless throughout the series and any one of the jlu members can take her down within seconds.