Spawn was king of the 90s.
Ubiquity.
I think the book suffered for two reasons:
1. The movie was pretty terrible and ruined perceptions.
2. Todd was too distracted by the business-side of Spawn to write a quality book overtime. He was too proud to hand over writing responsibilities to a quality author...and by the time he did hand it over, the boat had already sailed.
Todd took back over with issue 185 and has been trying to rescue the title, but I don't think his writing chops are up to the task.
I wouldn't say it's totally horrible - it's certainly no worse than most of its popular competition at the time, but I wish Todd would hand things over to some real talent with a solid vision for the character.
While I think Szymon Kudranski is the right artist for the job, I am getting pretty sick and tired of all the digital copying and pasting going on lately.
But anyway, back to this king of the 90s thing...Spawn by far. The title dominated the charts for a very significant amount of time in the 90s.
I will say that people who gave up on Spawn really missed out on some awesome covers....if nothing else, Spawn had the most wicked rad covers around (just check out issue 153, for example).
Spawn #1 is a more significant key by far - it was a game changer and the biggest selling independent comic of all time. It's just viewed as "trash" by speculators because there are a bazillion of them floating around.