Firstly i'd just like to say i'm a 20 year old man, so i grew up in the 90s, and i never read a comic in my life. Might have something to do with not living in the US.
Because of that i can't really voice an opinion on "cartoony cheese" over "darkly edgy" aside from taking it all at face value. Personally, i always found the notion of men in spandex beating up bad guys to be really... odd. (COMICS ARE WEEEEEIRD) I never understood the appeal of it. Nor did i get why comic book heroes were so popular when each one only had one or two powers and that's it. Look at the X-Men. Cyclops has his laser thing. Wolverine has his claws and regeneration. That blue chick can change shape. The point is i always saw comic book heroes as nothing more than pokemon for western man-children. Disclaimer: I actually grew up playing pokemon on the Game Boy, so i'm not really one to talk down to man-children. But the point still stands that to an outsider looking externally toward a culture predominated by man-children they're going to think it's weird, stupid and pointless - the one thing my mother always went on about when i was a young kid was how spastic pokemon was / is, for example, and no amount of trying to explain it could change her mind on that, and that's exactly how i feel when it comes to comic books and comic book heroes.
As i'm now a "mature adult" (or so i like to think) i tend to look at things like films for something that will appeal to that more eclectic taste of the gritty and mature themes that we as adults deal with and can now appreciate after having gotten out of childhood and puberty. Political, sexual and sociological themes are suddenly much more relevant to us, so we respond greater to them when it's presented to us in a film and why we identify so strongly with characters we recognise who go through those same struggles.
I've not seen the transformers films or even the X-Men films so i don't know how this merging of the cartoon comic and the gritty serious real world really works, though i have seen Sin City and Watchmen and loved them both. Aren't they examples of the above, of "comics not for kids"? That said, i and most everyone i know loved the Spiderman films, and they definitely had that pre-90's cartoon comic book vibe of a wacky city with a wacky hero and wacky (if emotionally and mentally unstable) villains, though that feeling did ebb away after the first film. Once Spidey has his powers, the tone darkens significantly as we no longer have the whole introduction-of-fantasy element in the way.