Not that I don't see what your saying, but I don't totally agree. Like in the above mentioned Wolverines case, while from when he started out he has increased in power he's one of the more grounded characters IMO. Second everything was in order he lost his adamantium and most of his healing factor. He gets his healing factor back and gets turned into more animal than man. Later on he gets his adamantium back but loses his healing factor. Plus you never see him 'hulking' up and lifting a building. That's partly why I like the character, because he's always battling an inner demon, and somethings always going wrong, plus he's never reversed time or went cosmic
. Plus characters like Cyke haven't really increased in powers, only their characters have been more fleshed out, well kinda. Plus they replaced former teammates like cable, bishop and so on with characters like maggot and marrow, while not bad characters their not uber powerful super saijin type increases to the team lol.
Now I do agree with you some characters are tho. Which is why I slowly like Hulk less and less. For awhile I tried to get back into him, but everytime you read he's a bit more powerful. He went on a craze of breaking all the comic rules, he bent adamantium, he stopped the Juggernaut, probably tossed the blob across the world or something....hmm what other rules can he break lol. Only thing he's missing now is superspeed.
But while the teen and up to adult comic readers might like their characters with flaws, the little kid audience tends to like the 'Oh! ****' moments where they reach never before power limits and do some rediculously stupid ultimate feat. Then the writers feel they have to keep topping that to make the readers come back. Least that's how I feel it is in my mind.