Awhile ago, on the usenet (Google Groups) newsgroup, rec.games.video.classic, there was debate on what was "classic".  Neogeo games were considered by some NOT to be.  And now, we have this thread on here:

http://www.vgchartz.com/forum/thread.php?id=73169&page=1

So, I would like to throw out there what would be a good working criterion for what would be considered "Retro", "Classic", "Old" or "Old school".  Please post your thoughts on this.  I would consider the following to be a measure for this (works now because arcades aren't relevant for discussion):

Any game that was released two generations or go, or earlier.  So, for now, any game released prior to the Dreamcast would fit into this category.  The Dreamcast fell right between Saturn/Playstation/N64 and the PS2, XBox and Gamecube.

Any game that harks back to a prior era, but was launched during that time would be considered "neo-retro" (I consider the new Lode Runner to be a "neo-retro" game.

There is usually a 10-15 year gap by this, and I believe this works.

So, what do you suggest?

2D graphics

Arcade style game play...ie, light on story and cutscenes, but heavy on fast paced game play. Easy to get into. Street Fighter 4 being a good example.

This is a myopic view, but may just tell us more about your tastes than anything else.  "Old school"/"Classic" games didn't really have cutscenes, sure.  But that didn't mean they were light on story. 

 Oh, and to the OP... Retro != Classic/Old School.

The cutoff for "classic" in the eyes of those who hung out on rec.games.video.classic back in the day was the video game crash of 1983.

Anything before that was classic. Anything after it was not.

However, as time went on, many started to consider games from the generation of games that immediately followed the crash as "neo classic."

Mike from Morgantown

Retro is before 3-D. I can't consider Mario 64 retro, because games like it are still being made.

Oldschool is either old games or new games in the oldschool style, like the new Punch-Out!! or Viewtiful Joe.

Trying to define this stuff is always a little weird, especially with the word classic. I remember hearing Pearl Jam on a "classic rock" station and being really confused. In art history classicism and neoclassicism are tied to specific time periods, so I always expect the word to work like that with music and games too. But that might just be me, I don't know.

You mean "criteria".

Retro, classic and "old (school") are found in the same area.  If you want to differentiate between them, feel free to.

I was asking to discuss this, because there are people who don't consider Neo-Geo games to be "classic" or "retro" or "old (school)".

Do you mean "before the use of shaded polygons"?  I would consider Zaxxon and Battlezone to fit into retro/classic/old(school).

If there are multiple elements for determining whether a game is or is not, that would be correct.  If it is only one (I believe I gave only one, that being 2 generations past), then it would be criterion.

Yeah that's what I meant.  Earlier styles of 3-D are definitely retro, like the 3-D games on Game Boy and even earlier.