MnM doesn't translate marvel characters easily. Those charts linked above are problematic. If you use them, unearthly = +10. That makes many MnM book characters with some very high marks in classic marvel. Also every superstat above the normal range is 20 base + superstat. Then you'll get a bunch of heros standing around saying 'wow you have three 20's just like me'.
I am creating something sorta like those charts but has a different benchmark for different things, as just as you see in saga each things is different when translating classic to saga and so to into MnM.
Plus you can use MURPG as a guide too, as they actually have some great write ups plus those you find on their forum. Its a base 10 system (rather than 20 like saga). I personally haven't played MURPG but it does look nice and seems to work.
But people like advancing characters and rolling dice. MnM seems to fit more with that. Marvel uses a more progressive style to power rather than a doubling chart, so in part you'll have to create characters with ranks, and then if they are ported into Freedom City world. they can run faster, do more, jump higher, etc. That is what they do in DC, pre-crisis where the heros were godlike.
Or that is partly the problem. Why are the players playing. Are they liking MnM cuz it gives you more to start (unlike champions), and then is the gm prepared to gm three or four little godlike characters who can throw around hordes of power.
I think marvel decided when it was created, that DC comics whitewashed things, and had what we might call a powergamer streak to it. So yes they set it the benchmark lower (and personally I think superman, the pre-crisis is a power-gamer character or rather the type of character a true cheese-hound would make if you didn't police him). So call that super-duper superhero rollplaying.
When you use MURPG and port over those pre-crisis superduper power-DC characters and you have limits like 9 actions you run into problems and simply have to ignore the system.
I also think that partly when it comes to characters like juggernaut if you set his PL fairly normal, but then are faced with how the math works in MnM if you max out, so that a PL 10 character can do up to 25s damage, and thus bypass even rank 15 protection and force a save, that in part you are deciding how untouchable to I want 'my version'.
Partly the use of such characters is 'examples', and 'benchmarks' for other real characters. But then you might actually use them as npc's or as player characters potentially. MnM is all about PL so that if you are a few PL higher you can truly be in another league.
So a lot boils down to how you the GM set your own benchmarks, and how you want your npc's and pc's to measure up relative to each other. Do you want to make a Strength rank 14 superman. And then you allow rank 15 characters. Don't be surprised when one of the comes to you with the rank 15 superstrength and base 20. I would not be. So they are basically making someone who is stronger than you set your superman at.
Centurion in the book is a cross concept character of superman/hulk. He has +20 rank (the highest on that listed scale) but can't fly, instead he leaps like nobobies business. Sure he is not exact but nestled in there is the concepts of those other iconic characters. Look in the books and those in part will be your 'benchmark'. So that a simple by the book conversion chart isn't exactly possible. Instead you start there and then use the books to tweek, at least that might be part of the answer.
Either steve didn't want to make it easy to do this process of converting or he simply didn't go out of his way to do so. I don't know but you can't simply sit down like you can with marvel saga or murpg and convert away.
Even using blood of heros (DC) is easier. Just the way I see it.
If you look at other threads and sites you'll see many other marvel style (and dc) characters, and there is a lot of guesswork involved or personal choice. So use those write ups or take them and tweek the for your own person use and campaign. Even if its simply to 'see how they did up cap's shield'. At least you'll have a use for it.