well, man, comics never really changed, they just reflected the times in which they created. In the 30's Superman counted as a character who is pure and was possibly created to as someone unnaffected by the depression and or something to give people hope. Captain America was one of the comics given to G.I.s in WWII for entertainment, kept clean, patriotic bordering on jingoist and possibly racist (if I remember how they portrayed the Japanese in the old comics correctly) to avoid issues like shell-shock, war atrocities, and the general futility of war. In the 50's the superheroes reflected the optimism and McCarthy Era paranoia that was going around, the communists being the next identifiable villain to nazis. The late fifties and sixties brought the occasional issue discussing race or drugs (the latter of which I know took up a Spiderman issue), where there were a few more black superheroes and what-not. The seventies being a slight rehash of the sixties only with a little more money and a little less soul if I'm not mistaken. Then the 80's came in with moral ambiguity up the ass for superhero comics, with obvious examples as V for Vendetta (i.e. what-if on Margerat Thatcher running the show in England), The Dark Knight Returns (an old hero going back to what he loved with less scruples in a more violent times), Watchmen (F&*#ing Watchmen!), and Nuclear Armageddon being a motif throughout these darker comics. The 90's brought a special brand of Cynicism and gallows humor with its even more edgier and experimental works, as in where Hellblazer becoming the amoral bisexual working class magician we all know (not just the guy from Swamp-Thing), the popularity of the Sandman comics gaining momentum, Garth Ennis writing about a narcissistic omnipotent deities and drunken alchoholic vampires and making the punisher not suck for the first time in a while, and the myriad branches of the X variety. The 00's and 10's are probably the same as the nineties but with an impending sense of impending doom in most of the comics with arcs such as Blackest Night or Dark Reign. I might be generalizing a bit, but I think the disilusionment and the loss of innocence reflects the the disillusionment of the people who both read and create the stuff. I prefer the darker stuff because it provide more room for flaws and therefore humanity in characters in the comics, and to sound slightly lame, darkness makes light shine so much brighter.
Man, this is not a choice since it appeals to personal taste. You like the Punisher for that, I like Deadpool because while the laughs he creates are funny, they are a mental barrier to hide a truly shattered individual. The guy hears voices for chrissakes, he was tortured in ways that the word pain cannot describe, he is actually cursed with life. I find a flawed action hero in Deadpool, and that's why I like him .
Well dude, if you want to get more good stuff with Batman in it, a good start would be The Dark Knight Returns by Frank Miller (possibly Batman: Year One by Frank Miller as well, but look for reviews first just to be safe), The Killing Joke by Alan Moore, and both Arkham Asylum: A Serious place on Serious Earth and Batman R.I.P. by Grant Morrison. I heard a few dissenting views as to the quality of R.I.P., but aside from that, the other comics are quite possible the best Batman graphic novels out. As for individual comics, though, all I know is to avoid, I repeat avoid, any recent batman comics done by Frank Miller.
as a side note: isn't there a batman graphic novel out there that got a manga artist to draw it?