Comics can be mysterious things. Trends, styles- they all come and go, but a few things stay stalwart. So, let's take a look.
1. Humble beginnings
I am going to use DC as a medium, so pay attention. In the late 50's the Flash was being revitalized by Carmine Infatino, and Green Lantern was taking new breath due to one of my favorite artists, Gil Kane. Soon the Atom and Hawkman collectively had their own titles. Even though there was short fluctuations, this idea of around 10 basic comics kept until the late 70's.
2. The Days of Prosperity
In the 80's all the way through the mid- 90's, there were tons of titles that rose and fell in popularity. Here are all the presently canceled comics I know of from DC, or ones that I know are going to be canceled.
Firestorm
Blue Devil
Booster Gold
Captain Atom
Green Lantern Corps
Green Lantern Corps Quarterly
Green Lantern: Mosaic
Guy Gardner: Warrior (sniff)
Lobo
Aquaman
Scare Tactics
The Spectre
Green Arrow
Hitman
Starman ( Will Payton )
Starman ( Jack Knight )
Hawk and Dove
Peter Cannon: Thunderbolt
Hammerlocke
Batman and the Outsiders
The Outsiders
The Darkstars
Hawkman
Eclipso
Team Titans
The New Titans
Teen Titans
Justice League International
Justice League America
Justice League Europe
Justice League Task Force
Global Guardians
Is that enough? If DC had known in 1980 that all these titles would be canceled, I seriously doubt they would have taken the advertisement campaigns and story turns they did.
3.Aftermath
Well, in 1996, the Justice League America franchise was dying, DC was cancelling titles left and right, and, well, everything was going to crap. DC tried one last desperate attempt, the Centennial edition comics,certain comics that had reached issue 100 that year, like Superman, Flash, and Justice League America. In the case of JLA, in the 100th issue they reintroduced Guy into the JLA with the "Return of a hero" storyline.
It failed.
But there was a beacon of hope- JLA. Grant Morrison and Howard Porter's JLA. It saved DC. That was the aftermath.