Let's see... you have gods/goddesses/demons/demonesses and their children existing in both Marvel and DC.
...and then you have all the other 'normal' supers.
Let's take the Scarlet Witch from Marvel for an example. In Avengers Disassembled, she nigh on rewrites the whole world, bringing back the dead (sort of), and defeating the majority of the team
Then you have Magician (or whatever his code name was), from Ultimate X-Men. If he thought something, it would happen. He wanted to become a part of the X-Men, so the world changed so that he would be taken to them directly.
Now let's take a look at DC comics. Superman, invulnerable to anything, revived after several days of being 'dead'. The Flash, capable of outrunning anyone and anything, amongst other speedy things.
There is no way any of the Tsukihime characters would be able to avoid having their very existence rewritten. TSW could probably do something like Warakia, except it wouldn't be vulnerable like the real one. Magician would just think them away. FSN characters would also fare the same.
Superman doesn't cast 'magic', so his wind breath/laser eyes/etc. would not be as ineffective against Saber as Rin's attacks were, and he'd beat the **** out of everyone else in the FSN cast. He's fast too, and he'd be able to defeat the Tsukihime cast... The Flash... well, let's see... Following spoiler is only tagged because it's LONG. It's not mine... but damn, is it good.
The Motherfucking Flash
Now, I don't know how many of you dogs of the scurviest sea read comics, but I do a big pile of comics. One thing that blows my mind is how completely insane the powers in the DC universe are. Look at Superman. This guy has more powers than French restaurants have ways to say "your taste in wine is atrocious". He has powers to do with every part of his body and then some. He forgets powers sometimes. He can shoot heat rays out of his eyes, frost breath from his mouth and red sun radiation from his ass. He's that sort of crazy dude. All because he absorbs solar radiation.
Look at Batman. His power? The anti-power. Sure, he should be some tame, kung fun master of not much, but instead he's the hottest shit to ever shit on a plate. You got a power? He'll find your weakness and give you seizures or heart attacks. He'll light you on fire when you're sleeping or make you recharge your green lantern ring in the power outlet. Ten thousand volts of fuck you batman. That's Batman.
But the fucking Flash, my god, my FUCKING GOD, this man has the greatest powers of all. If Superman's powers are being sucked off by twin super models and batman coming home to discover your wife is not only bisexual but has two friends she wants you to 'get in on' then the Flash is an orgy with a thousand women who also want to pay your World of Warcraft billing. And click the mouse for you. This man is just that fucking hot. They have to power him down in the comics half the time just to keep him from doing everyone else's job.
Ok first off, he can travel at lightspeed. Mother fuck! Not only does he travel at lightspeed, but time slows down for him. So he feels like he's having a casual jog or reading the paper, meanwhile, his feet are moving so fast you can hear him coming from Montana while he's already gotten to Arizona. That's fucking fast. But wait! The ability to move at Lightspeed just isn't fucking enough!
I know! Christ this guy can punch you so many times in a second you've been hit five times in the cock and two times everywhere else. You think you're about to fight the Flash and then it hits you, for the last split second he's beaned your beanbags with more blows than you had sperm. But no, there's more!
The Flash can also vibrate through walls. Now last I heard, you can not move so fast you can vibrate through walls, so what actually happens is the Flash is so fast he can pick and choose the movement of his individual molecules and move them through other solid objects, phasing through solid matter like it ain't no thing. I mean you think a guy who runs at lightspeed would run into shit but no, the Flash just goes right through them. To top that with a cherry and some whipped cream (which the Flash made in like a millisecond, fucker) he can selectively choose to cause objects to be "okay" afterwards or FUCKING EXPLODE. That's right. He can run through you and make you blow up by transfering kinetic energy into you. Like Jesus. IT's bad enough you can't hit this guy, but he doesn't even have to punch you. Now your testicles have exploded and you're thinking you're about to hit him. Jesus? Just give it up. He's the fucking Flash.
Now imagine that somehow there's someone who can get around the Flash blowing your balls up secret ninja technique. Ok. He can also control the flow of energy between objects. This power makes no sense but basically he can throw a rock at you, and you think it's going slow and then he's like WHOOHOOO WIZARDLY FLASH POWERS and bam it's going at lightspeed. So he can throw seven million rocks at you in a second then make them all goes different speeds thus striking your nads with seven million rocks one after the other.
But wait! There's more! He can also take energy from the very power of speed and make clothes out of it. Yes. Flash makes his pants out of GOES FAST. The man is so fast he can make Flash pants that GOES FAST go right into. I don't even start to understand the physics of that but basically SPEED == REALLY TIGHT UNDERWEAR AND COOL LIGHTNING THINGIES OVER THE EAR. You would think this is the end of it but ok let's say Flash is fighting Superman and shit he's going to lose and FUCK how is Superman THIS fucking strong? I don't know he must be Superman fused with Batman into some sort of guy with tons of plans on how to punch you far harder than anyone else ok to end it off the Flash can GO BACK OR FORWARD IN TIME ON COMMAND.
How do you beat this dude? You're thinking you're hashing him good, laying down the beatdown, missing your balls and suddenly BAM YOUR MOM FELL DOWN THE STAIRS TWENTY YEARS AGO and there's a dent in your forehead and Superman not thunk so gud no more. Actually she didn't fall down the stairs the Flash put speed into them so they fell up her! Fuck you Flash! You moved the stairs to Soviet fucking russia! RUSH-A! Bitch.
Oh, and lastly his greatest power is he isn't fast in bed. He takes it slow and gets all the ladies with his superpowers then actually satisfies them in the sack. Who the Hell is this guy? You'd think he could AT LEAST be a premature ejaculator since his penis is moving at lightspeed but NOOOO he's even good in bed.
And that, ladies and gentlemen, is why Wolverine sucks cock and should go die in a freak greasefire.
...Magician would have to think fast. But I still like the Marvel characters better.