I would say 1984-1992 Starting with Secret Wars/ASM #252
That's a very easy time period.
In alphabetical order , after "status*":
Major keys:
Albedo #2
Amazing Spiderman #300
Bone #1
Teenage Mutant Ninja Turtles #1
Keys:
Albedo #0, all firsts
Albedo #1, 1st & 2nd
Alf #48
Amazing Spiderman #252, 293, 294, 298, 299, 312, 316, 361
Batman #366, 368, 400, 404-407, 417-420, 426-429
Batman: The Dark Knight #1-4
Batman: The Killing Joke
Bone #2-8
Caliber Presents #1
Captain America #332, Annual #8
Crisis On Infinite Earths #7, 8
Crow #1-4
Cry for Dawn #1, #3 Horror, #5-8 Limited
Daredevil #227, 254
Detective Comics #575-578
Faust #1 Limited
Flaming Carrot #1
GI Joe #21
Gobbledygook #1, 2
Harbinger #0 Pink
Harbinger #1
I,Lusiphur #1, 3
Incredible Hulk #330, 340
Justice League #3 Variant
Magnus Robot Fighter #0
Miracleman #1 Gold, 1 Blue, 10-23
New Mutants #87, 98
Punisher Limited Series #1-5
Rai #3, 4
Sandman #1, 8 (both)
Secret Wars #8
Solar #10
Spiderman #1 Platinum
Spiderman #1 Gold UPC
Spiderman vs. Wolverine #1
Star Wars #107
Superman #75
Swamp Thing #20, 21, 37
Teenage Mutant Ninja Turtles #2
Teenage Mutant Ninja Turtles #3 variant
Tick Special Edition #1, 2
Tick #1
Transformers #76-80
Uncanny X-Men #201, 205, 210-213, 244, 248, 266, 268, 297 Gold, 303 Gold, 307 Gold
Unity #0 Red
Watchmen #1-12
Wolverine #10
X-Men #11 Silver/Platinum
Semi-Keys:
Albedo #0 Second
Albedo #4
Aliens #1, 2
Alpha Flight #51
Action Comics #583
Amazing Spiderman #249-251, 253, 265, 285, 289, 301-311, 313-325, 328, 330, 331, 344, 345, 362, 363, Annual #21 (both)
Animal Man #1, 5
Batman #436, 442, 457, 488
Batman: Sword of Azrael #1-4
Batman: Vengeance of Bane #1
Bone #9, 10
Captain America #333, 334
Crisis On Infinite Earths #1, 12
Cry For Dawn #2-8, #4 Limited
Daredevil #228-233, 238, 241, 248, 249. 257
Dark Horse Presents #24
Dark Horse 5th Anniversary Special
Death Rattle #8
Detective Comics #535, 569. 570, 572, 574, 598-600
Doom Patrol #19
Ewoks #1-14
Fantastic Four #320, #347-349
Faust #1, 2
Flaming Carrot #2-5
Flash #350, 1
Firestorm #61 Variant
Ghost Rider #1
GI Joe #26, 27, 93-96
Green Lantern #195
Green Lantern Emerald Dawn #1
Grendel #40
Groo Special Edition #1
Harbinger #2-6
Hellblazer #1, 27
Incredible Hulk #324, 331-334, 336-339, 341-346, 350, 367, 377
Infinity, Inc. #14
I, Lusiphur #2, 4-7
Iron Man #225
Justice League #1
Legion of Superheroes #37, 38
Longshot #1-6
Mage #1, 6
Magnus #1, 5, 12
Marvel Team-Up #141
Megaton #3, 8, Explosion
Miracleman #1-9
New Mutants #86, 88, 93-97, 100
New Teen Titans #44
Omega #1 Limited
Predator #1
Primer #5
Punisher #1, 10
Rai #1, 2, 5
Robotech: Macross #1
Sandman #2-7, 21, 22
Silver Surfer #15, 34, 35
Solar #1
Spawn #1
Spectacular Spiderman #90, 131, 132, 158
Star Wars #100-106
Superman #423, 50, 74
Superman: Man of Steel #17, 18
Swamp Thing #22-25, 34, 38-40, Annual #2
Teenage Mutant Ninja Turtles #1 2nd, #3, 4
Tick #2
Thor #412
Transformers #1, 70-75
V For Vendetta #1-12
Uncanny X-Men #221, 222, 225-227, 234, 256-258, 267, 269, 270-277, 281, 282, 283, Annual #9. 10, 14
Web of Spiderman #1, 18, 29, 31, 32
Wolverine #1
X-O Manowar #1, 4
X-Factor #6, 24
Issues of note:
Action Comics #584, 598, 683, 684
Adventures of Superman #463, 496. 497
Airboy #5
Akira #1
Albedo #3
Aliens #3-6, Vol 2 1-4
Aliens vs. Predator #1
All-Star Squadron #47
Alpha Flight #13, 17, 33, 34, 52, 53, 87-90, 106
Amazing Spiderman #254-261, 274, 275, 276, 281, 284, 327, 329, 346, 347, 359, 360
Animal Man #2-4
Avengers #263, 329
Batman #408-410, 416, 423, 433-435, 437-441, 450, 451, 465, 489-492
Batman: Legends of the Dark Knight #1
Bone #1 2nd
Caliber Presents #2, 15
Caliber Christmas Special
Captain America #300, 323, 328, 335-350, 366, 383
Cerebus #147, 161
Crisis On Infinite Earths #2-6, 9-11
Daredevil #219, 236
Dark Horse Presents #1, 10, 34-36, 51-62
Defenders #152
Detective Comics #566, 604-607
Doom Patrol #20-25
Elektra Assassin #1-8
Excalibur Special
Excalibur #1, 57, 58
Fantastic Four #250-292, 296, 321, 325, 358
Flaming Carrot #6-15
GI Joe #60
Ghost Rider #2-6, 15
Green Arrow Long Bow Hunters #1-3
Green Arrow #1
Green Hornet #1
Green Lantern #194, 200, 224
Green Lantern Emerald Dawn #2-6
Grendel #35-39
Groo #29
Hellblazer #2-10, 25, 26, 40-50
Incredible Hulk #300, 314, 327, 348, 368-376, 379, 400
Infinity, Inc #15-37, Annual #1
Iron Man #191, 192, 200, 226-232, 244, 250, 282, 283
Justice League #2-7, 18, 19
Kitty Pryde & Wolverine #1
Legends #6
L.E.G.I.O.N. #4
Mage #2-5, 7-15
Magnus Robot Fighter #2-4, 6-11
Marvel Team-Up #150
New Mutants #85, 89-92, 99, Special Edition #1
New Teen titans #34, 39, 42, 43, Annual #3
New Teen Titans #1 (Baxter)
New Titans #50-54, 60, 61
New Warriors #1
The Nam #1
Nick Fury vs. Shield #1-6
Omega #1
Omega Men #37
Poison Elves #8-10 (Mulehide)
Predator #2-4
Punisher #2-5, 8, 9
Punisher War Journal #1, 6, 7
Robin #1
Rocketeer Special Edition #1
Rocketeer Adventure Magazine #1
Rom #75
Rust #12
Sandman #9-20, 23-45
Shadowman #1-3
Silver Surfer #1, 36-50, 75
Spawn #2-4
Spectacular Spiderman #116, 119, 141-143, 159-160
Solar #2-9, 11
Star Wars #80-99
Superman #1, 9, 73, 74
Superman Man of Steel #19
Swamp Thing #26-33, 35, 36, 41-64, 84
Teenage Mutant Ninja Turtles #1 3rd, #2 2nd, #5-8
Tick #3-8
Thor #350-384, 411
Web of Spiderman #30, 38, 48, 59. 60, Annual #2
West Coast Avengers #1-4
Wolverine #2-9, 17, 41, 42
Wonder Woman #329, 1
X-Factor #1, 5, 40, 41, 42
X-O Manowar #2, 3, 5, 6
* How I determine "status": recognition + popularity of book + popularity of character + value. Not everyone may agree with all placing, but it will be close. Books that are expensive, but not necessarily recognized (like Albedo #0 first printing variants) aren't going to be "major keys" and so forth. Likewise, a book may not necessarily be very expensive, but may be immensely popular, to be considered a "key" (a la X-Men #248.) Status can and has changed over the years.
(if you see an issue missing, check the date range given. It might fall out of that range.)
Did I forget anything....?
Holy ! I'm impressed....