While not the perfect translation, superman is a paladin and batman is a rogue with a smattering of monk.
The issue arises when you look at things from a purely combat angle, supes is specced almost entirely for combat, he convinced the GM to let him trade out his spell list for an OP outer planes species that has flight, a few innate at will spells(scorching ray heat vision, cone of cold ice breath, haste superspeed, scrying Xray vision, disguise self clark kent, ect...) resistance to standard damage but is vulnerable to magic and cold iron kryptonite, 20 STR, 20 CON, decent CHA, and averageish DEX, INT and WIS, But now bats on the other hand, bats is basically built entirely the other way around, his stats are lower because of multiclassing and taking feats instead of ASI, they’re more equal across the board 12s-16s with more focus on DEX, INT and WIS, only he’s got reliable talent plus the skilled feat to get bonuses to stealth, acrobatics, investigation, history, perception, survival and intimidation, plus a ton of starting gold from his noble background that he uses to supplement his abilities even further by buying magic items tech.
So Supes and Bats are not balanced in a fight but they are balanced across the whole campaign which is what really is the important thing to achieve, they’re not meant to be put against each other head to head they’re meant to support each other as they fill different niches in the party dynamic and they both do their own role well
Edit: it’s also to note that Supes and Bats are originally both the protagonist of their own media separately before being brought together in the justice league whereas frodo and gandalf are part of the same story and play entirely different roles within it, frodo is not meant to be anywhere near the same level of narrative power as gandalf is.