What I am about to say would seem to go against the accumulated genius of two of Superhero gaming's brightest and most experienced minds. I could be looked at as a fool, a heretic or simply a madman. This is nothing new for me. I disagree with genius all the time. Just ask Zak.
Today is different though, for today I openly disagree with not just Genius but Super-Genius! And not just one Super-Genius mind you but two Super-Geniuses!
Steve Kenson is, for all intents and purposes, a living legend in the RPG industry and a master of the Superhero RPG in particular. At 43 (as of this writing - the same age as yours truly), he was worked on nearly every major Superhero game system out there including Aberrant, Champions, Marvel Super Heroes and Silver Age Sentinels. He is the creator of both Mutants & Masterminds for Green Ronin and ICONS for Adamant Entertainment.
Cam Banks is the Creative Director for Margaret Weis Productions and the creator of the innovative and awesome Marvel Heroic Role Playing Game, which uses a version of MWP's Cortex System.
I want to begin by saying both of these men are brilliant. These guys have talent up the yin yang and I love their work.
Deep breath now...
Both have noted, at one time or another in the recent past, that in the Superhero genre...actually...specifically in comic books, Superheroes rarely increase in power or improve in the way most role playing game players expect. That is, unlike a typical D&D character who gains more hit points, new abilities and better skills as they raise in level, the comic book Superhero really doesn't change that much over time.
Oh sure, they may dramatically change for a short period of time, such as gaining a new costume or receiving an alternate set of powers because of the current storyline but generally speaking, character improvement of the type we gamers come to expect is rare. Characters seem to change horizontally but they don't often climb vertically.
This is reflected in ICONS to some extent but much more so in Marvel Heroic. There really aren't major rules for improvement of a character's abilities, although there is definitely experience point awards as obtained through personal or plot generated 'Milestones'. These can be used to buy new powers sets (swapping out an old one for a new, alternative one) or make certain minor improvements.
After all, Spider Man, Superman and Iron Man haven't really changed since their first appearances.
Spider Man always spun webs, had spider sense and was pretty bright.
Superman always flew, had super strength and heat vision.
Iron Man's armor hasn't really improved or changed in capacity in the last 45+ years.
Spider Man failed to save Gwen Stacy when she fell from the George Washington Bridge because the way in which he attempted to catch her (webbing her leg) was insufficient to prevent her neck from snapping at the height and speed she fell from.
These days, we've seen Spidey (numerous times recently) spin massive web 'nets' and catch literally tons of falling debris to prevent it from crushing the citizens below. It would seem he has become more adept at the use of his webbing. He is more experienced and skillful.
Initially, Superman couldn't fly. Rather, he leaped tall buildings in a single bound. His massive jumps were pseudo-scientifically explained as similar to a Grasshopper or other insect leaping many time it's height do to his vast strength and gravitational differences between Earth and Krypton.
Created in 1938, Superman would not have heat vision until 1949. His X-Ray vision was used in one story to melt ice. By 1951 he gained heat rays from his eyes dubbed heat vision that were clearly separate from his X-Ray vision.
Super Breath, Ice Breath, Super Hypnosis, Super Ventriloquism - For a time it seemed like Superman had a new power every issue. When I one brought this up to my friend and Champions mentor Will he explained it quite simply, "He was saving up his XP. Then he started spending it and he bought new powers."
Iron Man's current armor has a force field. I have been an Iron Man fan since the David Michelinie/Bob Layton days (beginning 1978) and when I saw this recently I was like, "Wow." His armor was also unaffected by the magnetic powers of Magneto in their recent tussle in Avengers Vs. X-Men. I remember them meeting in the past and Magneto messing up the Golden Avenger.
These aren't just isolated examples. While some characters might stretch the point more than others, I think it's both apparent and relevant to say that there is considerable evidence within comics to show that Superheroes do indeed improve. Therefore, a desire and need for them to improve in a role playing game is not outside of the genre as it is presented in its source medium.
I would also point out that we are not creating comics, we are running games. Gamers, more often than not, like to see rewards for their efforts. The feel and atmosphere for a Supers game should definitely reflect what you get from your favorite comic books but in the end it is an RPG. The PCs don't often get paid, they don't kill Capt. Cold and steal his Ice Ray Pistol or anything like you'd expect to get points, magic or specialty items or similar rewards for. Experience points are pretty much the one and only key way of saying, "Thank you Super Person! Job well done."