Too many to list.
Back when I was in college, Roger Stern didn't live far from me (his wife was a chemistry professor) and you'd see him around the local comic book shop all the time. In addition, because this was when he was a big deal at Marvel, whenever they had the local convention, you'd get a fair number of Marvel's "big guns" at time.
Among the guys I specifically remember: Shooter, Byrne, Denny O'Neil (this was when he was writing Daredevil I think, right before he went back to DC), Jerry Ordway (working with Byrne on FF).
Shooter was a really nice guy to the fans, probably the nicest creator I ever met. Byrne was a little standoffish but still a decent guy. O'Neil was an interesting follow but a little like talking to your dad, given how much older he was than everyone else. Ordway was kind of dick. Stern was a nice guy and, if anything, talked too much. He's like the party guest who has a great story but can't wait until someone else finishes their's to jump in.
Non-Marvel guys about the same time: Tom Mandrake, Jan Duursema (she was really friendly and approachable, him not so much), Curt Swan (friendly guy, I think he had hearing issues), Len Wein, Marv Wolfman, and Dave Sim (Dave hadn't gone completely nuts yet).
A couple of years ago, I met Neal Adams at a convention. The only guy I've ever paid for an autograph. I had him sign a couple of Batman hardcovers of his work and an old DC treasury edition he did the cover for (that I still need to get framed). He was a very friendly guy but I was so intimidated by meeting "the Batman artist" of my youth. That, and the fact, he kept wanting to talk about (and sell copies of) "Batman Odyssey," made it a little difficult to have a conversation with him.
Last, but certainly not least, in the late 80s, I went to the NYC Comic-con, stood in line for about an hour, and got to meet Stan the Man himself. I had Stan sign my ancient copy of "Origins of Marvel Comics." He seemed really touched that I asked him to sign something that he could tell I'd owned since I was, in his words, "a little boy." Loved meeting Stan and hearing Stan's voice in person.
