Actually, the inspiration came from a lot of different sources. Sadly, I realized that most comic characters, especially once they get their own TV show, end up being epic-level in power. In my mind, the breakdown went like this:
Average mutant/one-shot villain: No more than 5th level. Examples would be, say, Toad from the comics, or most of the Morlocks, or a local mafia boss. Average people still have a chance against these guys, if not a good one. Oddly enough, most of Batman's villains probably don't get past this stage, which means they have to rely on cunning plans and thugs to handle the caped crusader, since they have no chance to take him on one-on-one. Thus, it's important not to always base XP awarded on the physical challenge the villain poses, but on how tough they are to outwit.
Average street-level hero/villain: No more than 10th level. Examples would be DareDevil, Marrow, Robin, Poison Ivy, or Killer Croc (he's tough only when he's in his native element, water; otherwise, Batman whips him good). These guys are too tough for average people to take on, and so have to be challenged by 'main characters.' Someone like Bullseye or Nightwing would probably edge up to 15th level or so.
Superhero/Supervillain: Around 20th level. These are reaching into the larger-than-life characters, the ones who have become semi-iconic. Spidey's here, as are the Green Goblin, R'as Al'ghul, Witchblade, or heck, Lara Croft.
Champions/. . . um, Anti-Champions: 30th to 40th level. These are the epic characters that it seems nothing can kill, and the overarching villains who can challenge them (or at least large teams of lesser superheroes) over and over again. Magneto, Superman, Batman, Professor X, the Hulk, Captain America, Thor, and Bugs Bunny.
Guys You Don't Mess With: These ones you don't even bother making levels for. Folks like Galactus, Apocalypse, and so on. They just do whatever they want, and the only way to beat them is to figure out what the GM wants you to do.
As for prestige classes, I had a few archetypes in mind when I revised Russ's original drafts.
The Detective is Batman. Particularly his power to go into hostile territory and get the info he wants without having to fight anybody. Of course, he also does have Menacing Vigilante, but it's not as intrinsic to his character. All Batmans (even that 60's Batman) are detectives, but only certain writers really make him out to have a hatred of criminals. I was weaned mostly on the Paul Dini Batman animated series, so my Batman would come mostly from that source.
Animated series Supes was probably 30th level, so I'll put Batman there too. As such, he'd be a Specialist 6/Fighter 4/Monk 1/Rogue 10/Detective 4/Menacing Vigilante 1/Hero 4. His Hero Points go toward Heightened ability scores, and gadgets. Someone mentioned the concept of an Omni-gadget power, which basically gives you plot carte blanche to have whatever gadget you need, though the cost is higher than normal. He'd definitely have that too. Future-world Batmans (Dark Knight Returns, or Kingdom Come, or Batman Beyond) also grab a few levels of gadgeteer.
The Gadgeteer was Tony Stark, for Iron Man. Sadly, I was never much of an Iron Man fan myself, so I had to rely on the advice of some of the gamers in my group to come up with some of the prestige class abilities. Also, toward the end I'd gotten really fond of Cog (he might be my favorite part of the book), so I wanted to make the class have powers that would work well with his character concept. Tony Stark would be something like a Specialist 4/Fighter 8/Hero 10/Gadgeteer 8.
The Menacing Vigilante is the Punisher, and maybe also a little DareDevil (in his darker moments). And of course Batman, from time to time. The Punisher would be a fairly straightforward Fighter 7/Menacing Vigilante 5.
The Mentor is . . . well, to Russ, he's that guy who teaches Buffy. To me, he's a mix of Professor X and Alfred Pennyworth. For the record, Alfred would probably be a Specialist 5/Mentor 5. Afterall, he was in the British secret service, apparently.
One section I wanted to write but that I couldn't pin down properly at the time was advice for giving Villains the Leadership feat, as an excuse for how they keep getting all these henchmen, and for how they can arrange to have all kinds of nifty gimmicks. I'm thinking primarily Batman's rogue's gallery, how they always have some sort of plan that fits their style . . . how did Two-Face get the giant penny? when did the Penguin build his Aviary of Doom? how did the Scarecrow get ahold of an airship? I wanted to have advice for letting the Leadership feat represent sort of villainous or heroic resources, but I couldn't figure out a good way to explain it. The closest we get is mentioning that sample NPC Cog often has a pair of Iron Golem henchmen.
