A lot of people have fond memories of their younger years reading comics, and I am no different. I have blogged about this before wrt to European Sci-Fi.
Just as influential however were American superhero comics. I just devoured them with an ever increasing voracity, partially because they just offered such grand scale ideas! (Which is part of the fun of Sci-Fi for me)
The period that spoke to me most was the late 70s/early 80s Marvel era, especially the work of John Byrne.
John Byrne worked on all the greats; Fantastic Four, X-Men, Avengers, Spiderman… you name it, and often gave them new life with seminal issues. His work with Chris Claremont on the X-Men or his superb Fantastic Four run defined the era for me.
He could easily compete with the less formulaic European scen though, if given the freedom. Check out this rare example (Critical Error) couresy of the Space in Text blog:

Its the super hero stuff that did it for me though. Be they classic characters or new heroes or villains Like Terrax the Destroyer who was such a good character in the Fantastic Four:

Ultimately what really makes his work stand out is that it is always inventive, full of colour and ideas, without being overly shouty or pin-up influenced. Somehow it feels both iconic and modern.
I am not sure if anybody produces superhero comics quite like that anymore, but I would love to find some.