I have Frank Miller’s Wolverine mini-series and I don;t know if this counts, but I started collecting the X-Men right before the Phoenix Saga.
Great Caesar’s Ghost, the definition of Legendary is all across the board.
Here’s my entry…
Don’t know how “legendary” it is, but I have the first five issues of “Ghost Rider.”
For what it’s worth, I bought them all for the cover price when they were new.
What was the cover price you paid for them? Different editions had different cover prices.
Hmmm, strange how a comic book blog has a lot of discussion about comic books. 
For a comic book nerd I don’t have a lot of things I’d call “legendary”. I did collect the Flash/Superman races from silver age, the Inferior Five, and I’ve got the Jerry Lewis issue where he meets the Flash.
Alan Moore’s Swamp Thing. Actually I have all issues of Swamp Thing, all of the series, even the latest not so good ones.
As many, The Killing Joke.
First Hobgoblin, Amazing Spidey #238. Tattooz intact… 
First print Sandman series by Gaiman.
The Claremont/Byrne X-Men issues.
Marvel New Universe 
I don’t know if it counts, but I’ve got the first Sonic the Hedgehog. I bought it for the price on the cover and it has gone up a lot in value. It’s about the only thing I’ve got from the prospector era that has gone up in value.
I have, from the late 60’s, quite a few Fantastic Fours, X-Men, Mighty Thor, and a few others…Conan the Barbarian for the flabbergasting artwork. I LOVED Marvel Comics when I was a young girl and haunted the Rexall Drugstore waiting for new ones. I even had Millie the Model and the Rawhide Kid!
(Yes, my mom threw out my humongous collection and yes, I could have retired in style after selling all those rare issues…just have a few of my favorites for the memories, though the stories are kind of dorky decades later.)
Superman #17, with Supie holding up Hitler and Tojo by the scruffs of their necks. July, 1942
Uncanny X-Men #141 (Days of Future Past) is probably my sentimental favorite
I had an old beat up copy for as long as I could remember, but traded it to a friend somewhere in Jr. High. A couple years later I bought a nm copy at a convention for $9.
Also, a lot of the original Mirage TMNT comics. Not first printings for 1-3 though. I think my #1 was 3rd print (still oversized!), and the others were 2nd print. 4 on were all 1st print, though. That was a big deal back in the day, which printing your TMNT’s were, lol
Rob Liefeld’s Youngblood, #1. Featuring the Middle-Eastern dictator “Hassam Kussein”.
The cover price on the editions of Zap #0 and #1 I have is 35 cents. The cover price on Zap #2 is 50 cents.
Let me think…
The Tick #1 and #2, limited editions (print runs of 5000 and 3000 copies, respectively). I also have first prints of issues #3-8.
Frank Miller’s run on Daredevil.
Walt Simonson’s run on The Mighty Thor.
First prints of Teenage Mutant Ninja Turtles #4 and #7, plus first prints of the Raphael and Donatello one-shots.
I only have the second print of The Killing Joke. You can tell which one you have by the text on the cover; as I recall, the first printing is red, mine (if I’m remembering right) is purple, and later printings are green or other.
Couple random Amazing Spideys, pre-30. Like, 12, 17, 21, or something like that. Good to V. Good.
Star Boy’s first appearance, Adventure Comics. (Horrible shape)
For The Man Who Has Everything (Action Annual… 10?) Good. Bought it new, read it quite a bit.
Entire Alan Davis run, Excalibur. Most of the Claremont X-Men, including Days of Future Past.
Crisis On Infinite Earths, original issues, mintish.
Watchmen, original issues, mintish.
Tick, first or second printing (the outsize ones) good shape.
TMNT, 2nd or 1st printing, first ten issues or so.
Spawn #1, for some reason.
Random stuff. If it’s from the last 20 years, I probably have it. If it’s from the 60s… I have some of it.
Reprints: I have about ten feet of Essential and Showcase reprints, and various trades. Maybe more than ten feet.
Things I do not have: Underground Comix (Except some Wonder Warthog), and Sandman. (I do have Death: The High Cost of Living)
Lesse. Death of Superman, first appearance of Venom (Web… 99? The Spot was in it.), first credited appearance of Venom, first Deadpool, most New Mutants of the classic era, Astro City’s first twelve… lots of Journey into Mystery and Tales to Astonish…
Captain America #100
Avengers #4
Both are part of a huge-ass Captain America ‘stuff’ collection.
…and we have a winner. I am not even a Man of Tomorrow fan, having grown up in the heart of the Silver Age as a Marvel kid - but that just sounds cooler than cool.
Here’s a picI found on line. How Old School is that?
Obscure, but arguably legendary IMO, I’ve got the first run of Brian Talbot’s Adventures of Luther Arkwright. It was steampunk awesomeness before steampunk was ever a genre.
Just Preacher #1. Bought it when I was briefly trying to get into comics as a high schooler 'cause a few of my friends were into 'em. (Course, I screwed it up by going for comics no one else read. ;)) Sadly its not in the sort of condition to be worth much, though it’s in good condition for non-collectors… but it’s a nifty thing to have.
LOL, I have that one too.
My dad - an extremely straight-laced accountant - somehow ended up working as the CFO for a comic book distributor back in the mid 90s.
Good times. My extremely “Grey, black or navy suit, every day. No exceptions.” dad ended up having both a “Punisher” and an “X-Men” poster, framed (very tastefully!) in his office.
Funny thing - he tried to get me into comic books. Yes, my middle-aged, conservative, accountanrt dad tried to get me into comic books. I was maybe 13. I resisted, because, you know, it was my dad. A pity.
Never really got into them. The company folded late 90s and my dad moved on.
But I do have a “Death of Superman”. I remember my dad telling me it would be worth something someday. It’s probably still collecting dust in my old bedroom in my parents’ house.