^I think being able to play as Lex Luthor could be a fun thing to unlock for a Superman game. I don't think that Lex Luthor makes for very good gameplay. I don't know of many crafting action games, for instance. His intellect is what makes him special, and you can't really give that kind of creativity to a player in a video game, afaik. And it also reeks of defeat. But if it could be done, it'd be interesting.
As a last point on power levels, like you said, you'd have to make the villains stronger. But why do that, when you can use a lower levelled or even just younger Superman? This way you can have a Superman with standard level enemies (like Batman's thugs) and it's more of a challenge to beat villains.
I don't want to fight thugs as Superman. Maybe that's just me. I also don't like it when cities are overrun with world-changing forces but the world is not dramatically changed.
Making the villains stronger makes you feel more powerful when you defeat them, tuning everything down to make a Batman game doesn't seem like the best use of the IP. It's one thing to start weak and build up, it's another to make that the theme of the game.
Anyway, for powers I'd use:
Flight (activated with double tap of X/A controlled with both analogue sticks)
Super speed (hold L2/LT)
Super jump- to help get to a higher point for flight (hold then release X/A)
Heat vision (R1/RB) hold L1/LB to focus.
Microscopic vision (hold L1/LB)
X-Ray vision- must be switched out with heat vision ala Bats gadgets (R1/RB)
I'd also have a solar energy bar, depleting all of it means no access to super speed, vision powers, strength is reduced. And you need to charge up. Just to make it a little more difficult.
Invulnerability would level up as you progress through the game.
Level 1- Regular bullets do incredibly little damage, it would take tens to kill you. However explosions from missiles/tanks would do more damage, it would take about 10 to kill you. Kryptonite exposure causes health to drop dramatically and reduces solar energy. Energy attacks from Brainiac are severe and take about 6 to kill you. Super punches don't do as much damage, they take around the same as missiles.
Level 2- Damage decreased by 15% (energy by 10%), bullets do no damage unless exposed to Kryptonite. Kryptonite itself has less effect.
Level 3- Damage decreased by 20%. Only Brainiac, Doomsday and Zod can cause major damage that they're still a threat. Omega Beams take away huge swathes of health.
All other powers increase over time as well, more fine tuning for heat vision etc.
Sounds very cool, I'd probably give every power, even Invulnerability, five different levels/options to unlock, but those are definitely the types of changes I'd be thinking of.
Combat with bosses I think should largely be handled with QTE's like the Factor 5 game.
I don't know about largely, unless QTE is handled in a more robust tactical way, it works best for cinematic finishers, like in God of War.
Basically make Metropolis a living, breathing type of place except like in Arkham City, just have him use his super sense to locate various disasters happening around the city, and have some of them happen simultaneously so you have to make decisions. Though it may be possible to avert all of them, you have to be pretty ****ing impeccable in order to make it to each one.
That's probably the best analogy to Batman's stealth challenges, but that's not enough to fill out a game. In fact, it actually might create the Superman Returns "please please punch something" effect, if that's the basis of the game.
Start it off by doing everyday Superman things, build up the players' ability to control Supes' power. Something happens taht he needs to start investigating as Clark that he knows runs deeper. Then slowly build to reveal the big villain in a showdown. I think having a mix of regular day Supes where strength is not too important or even where you have to be careful of your power the way Supes actually does, contrasted with the end where you really need to 'let loose'. I mean, take advantage of the problems Supes has, like the way that Arkham City takes advantage of the problems Bats has. They're quite different issues, but both can be explored effectively in a game. Have the option to change from Supes to Clark any time, make him have to go to a press conference as Clark for LexCorp. Oh ****, looks like Lex is up to something: Gotta go investigate further, etc. Don't want to? Blow it off, have side missions that you can ignore if you want, but have an incentive system that rewards you for actually helping. Ugh. I just want this game to come out already, haha, it sounds like a great Supes experience to me, mixing together all the elements we've discussed. The possibilities are endless. But I do think taking it back to STAS like stories is the way to go, while obviously making them more complex and bringing in tons of cameos that fit into the world/plot like Arkham was able to. I don't see how that formula wouldn't work in the right hands.
I never understood how being Clark Kent, or otherwise trying to avoid using your power was supposed to be fun. Batman also has problems where he has to avoid showing off that he's really Batman, but that doesn't make for a fun game for people who want to do the cool things Batman does, so they didn't put it in. Some STAS stories make for great missions, others, which are entirely about dialogue and character development, would certainly not.