Although we'd really miss out on some great stuff, I'd say 1983. No Crisis, no Secret War. The crossover madness had not yet set in, and we had JB on FF, Miller on Daredevil, Perez on Titans, Giffen on Legion.

Hope that answered the question.

1979

Marvel:

ROM:Spaceknight set in the 21st century. Spider-Man still in grad school, with cameos by The Punisher, and the 1st appearance of the Black Cat, in a 21st century setting. I may be wrong here, but Captain America still partnered with the Falcon. Regular one-issue, complete team-up stories in Marvel Team-Up and Marvel Two-in-One. You could still keep up with the X-Men by reading one title a month! Was She-Hulk around yet, or was she a 1980-introduced character? The Invaders are still around. Fun times, and it would be a great challenge to place these, and many more, Marvel properties from 1979 in a modern setting.

The downside of this thought exercise is that rewinding to 19XX doesn't mean that today's talent would write as if their next issue were 19XX + 1 day.

Putting Peter Parker back in high school just means that's the jumping off point for JMS. 

Grant Morrison, Geoff Johns, Brubaker, Bendis and the rest will write the way they write, regardless of how the chess pieces are set up for them.

Hello all,

Sept/ Oct 1980 at Marvel.  You had:

X-Men 137/ 138 (Byrne)

Avengers 199/200 (Perez)

Cap 249/250  (Stern & Byrne)

Conan 115  (Thomas & Buscema)

Thor 299/300

Iron Man 139/140  (Layton & Michelinie)

FF - However, were not good at this time. 222/223

I loved the Toys R Us  & 'This Comic Might Be Worth $2500 To You' banners at the top as well. 

Thanks for reading

I, too, would put both companies back to 1982.

For Marvel, you had such stories as "The Death of Captain Marvel" and "God Loves, Man Kills".  Plus there was some new guy called John Byrne on Fantastic Four.

For DC, no Jason Todd, Captain Carrot was being published, Levitz & Giffen on Legion.

For both, there was a little cross-over between 2 little known teams called the X-Men and The New Teen Titans drawn by Walt Simonson.

I have to agree with John Wyatt.  Take whatever favorite character you may have and drop him or her into today's modern comics world, and you have a lamb in an abattoir.  There isn't really a character I had more fondness for than the Roy Lincoln Human Bomb.  Growing up, I "got" the loneliness and isolation of the character and his plight, and I liked that he had a team to hang out with in spite of it all.  The character had history, having debuted in the same issue of Police Comics with Plastic Man. He used to pal around with a guy named Hustace Throckmorton who had explosive feet! He wasn't overexposed. I liked his low-tech costume and appearance.  His existance on an alternate earth. Everything.  I liked everything about the guy.  And I never once pined for his reappearance in a modern comic, because I knew what I would get.  I would get what I got when he and the rest of the Freedom Fighters showed up in Infinite Crisis.  A death scene.  A fairly clever one, one that was not badly written, taken on its own terms, but a death scene.  Because Bizarro, and Black Hand, and Grodd, and every bad guy you ever met is a mass murderer today, and any character with the slightest notion of nostalgia clinging to him or her is marked for immediate death or "reimagining."  There is a Human Bomb in the DC Universe today, some sort of paramilitary badass with a high-tech armored suit and a history of criminal wrongdoing, if memory of the one issue I've read concerning the new team serves me correctly.  But I don't care.  I'm not railing from the rooftops or conducting a private boycott regarding the matter.  It is what it is.  I'm certain the new guy has his fans.

So the Peter Parker of 1976 or 1983 or even 1966 would be subject today to the same level of consideration by the current crop of creative personnel.  It would be necessary to "sharpen him up," "get some dirt under his fingernails," "take him apart and see what's left once you strip away all the dross..." Having reset Peter to the character he was in 1973 would not isolate him from storylines like "Sins Past" or "The Other." He'd just be a little bit easier to work with at the outset.  Within a short period of time, he'd be every bit as morose and streetwise as any character in existence today.

The premise of this thread as outlined is not a science fiction concept.  Walt's Thor and every story you ever enjoyed would still exist, nothing would be "lost," (shades of the voices of the first Crisis mini). The comics of July 2008 would simply start off as accessible and well-considered as the books of yesterday were.  But the idea does lose steam when one tries to imagine that the writers of today could, even if they wanted to, manage to write in a style that left the characters in a usable condition for the next team.  They can't.  They wouldn't if they could.  Every "important" team distorts the concepts to suit their own creative vision, and the next team must either expunge that interpretation, carry on with a severely altered status quo, or simply "ignore" months of continuity to chart their own course.

For me, personally, I think the characters clicked and were suitable for any story you wanted to tell with them as late as 1983.  1979 was when I was rolling along, getting my bearings on the various companies and their histories, and there was nothing in the current titles saying "ignore that whole section" or "Oh by the way, this guy murdered someone in 1947 and we're only telling you about it now."  Glitches and gaffs occured, but they weren't fatal.  They were honest mistakes, or goofy sideline events.  A cut-off point anywhere in that era would work for me, but the newly-reminted Don Blake of today would still be facing an emergency room filled with the victims of the latest thing like Civil War and squaring off against a steroid-hyped El Toro Rojo who's mission is to snap the spine of every 13-year old girl in a certain neighborhood because his supplier's cut him off and has a child that age... And Jane Foster would be suffering from a sexually transmitted disease... Jane Foster, dying of "Syph"... Ironic, really... so damned ironic...

So just have all the issues start out with the Watcher waking up from a bad dream?

Seriously, I would pick about a year before Secret Wars for Marvel

DC? I don't know it well enough to pick so I guess I will say at the JB Superman reboot or shortly after.