I've got some "collectable" issues, but none are professionally graded so aren't really worth much. I've got some Silver and Bronze Age stuff but most of what I've bought in recent years are good condition versions of some of my favorites from the late '80s to mid '90s that I wore out/damaged before I knew any better. Vast majority is Marvel X-Men and related.
Graded and encapsulated I might have $600-$1K, but I'm never going to pay to have them graded.
Ony Graphic Novels I have are Dark Horse's various Alien stories and Aliens Vs. Stuff, i.e. Predator, Terminator, etc.
Some highlights of my collection:
The Uncanny X-Men #222 1965 (Wolverine battles Sabertooth)
The Uncanny X-Men #184 1963 ("The Past of Future Days," 1st appearance of Forge)
The Avengers King-Size Annual #10 1981 (1st appearance of Rouge, Brotherhood of Mutants takes down Captain Marvel)
The New Mutants #87 1990 (1st appearance of Cable)
The Uncanny X-Men #221 1987 (1st appearance of Mr. Sinister)
Ghost Rider #1 1990 (1st issue of 2nd series)
Venom: Lethal Protector #1-6 1993 (Stand alone limited series)
Venom: Funeral Pyre #1-3 1993 (Venom & Punisher limited series)
Venom: The Madness #1-3 1993 (Venom vs. Juggernaut limited series)
X-Men #1 1991 (I've got all 5 cover versions that go together to make a panoramic poster)
X-Men #4 & #5 1991 (Omega Red, one of my favorite bad guys)
Spiderman 2099 #1 1992 (Not worth much, but I remember reading it cover to cover when new while mom was shopping)
Spawn #1 & #2 1992 (They made enough of these everyone has a 1st edition)
Wolverine #50 1988 ("Codename: Wolverine Top Secret," not worth much, but cool cover with claw holes slashed in it)
Aliens: Stronghold #1-4 1994 (Space Marines Vs. Aliens, plus a foul mouthed, cigar smoking, machine gun toting, synthetic/android, xenomorph developed to infiltrate hives, what's not to love?)