I think we all know that "realism" in super heroics just means "lower power level". It's not more realistic at all, as you said.
I liker all sorts of power levels.
I think the problem with Superman is context. I love a lot of the early Golden Age stuff where he's not that powerful compared to what he was later or to later heroes. But he was the top of the heap at the time. Well, okay, the Spectre. But I don't think that, in those early days, they thought of different characters as existing in the same world just because they were published by the same company or even written by the same writer. If it happened in a Superman story, then it existed in the world Superman existed in. So, Normal Man x 10,000 only works in a world where everyone else is even less than that.
On the subject of Unbreakable (and I have not seen the sequel), I really liked it and I thought what was particularly appealing is that trick that you never actually saw him do anything superhuman. It was always just implied but nothing you actually saw was undeniably superhuman. And, before anyone (not you) mentions the train, you never saw it.