Spy vs Spy

Remember the comic strip Spy vs Spy from Mad magazine?
Back in 1984 it got a video-game,
It's great fun to play against a friend, and it was most likely the first split-screen game ever made.

The game takes place in an embassy and the object of the game is to find a number of items, and then exit to the airport. The one who does this first wins the game.
To be able to carry more than one of those items, you need a briefcase.
All items are randomly hidden around the embassy.
The players also have a variety of traps that can be rigged in the rooms. Also hidden around the embassy are tools that can be used to counter the other players traps.

You can get a copy of the Atari/C64 version for around €13.
A used copy of the NES version goes for about €7, but if you are lucky enough to get one still in its original packaging and plasticized, expect to pay closer to €100.

What is retro gems?

I have been thinking hard about this blog. Of course I would like to make it as interesting as possible to read, but what really constitutes a "gem" of a game?
Furthermore how do you really define "retro"?

I think it would be appropriate to define retro as any game that was released to a console at least two generations past. In other words Playstation 2, Sega Dreamcast and other 6th generation console games.
Now, the last games to be released for the PS2 was PES 2014, in 2013. That's not that long ago.
Is it really fair to use the same measurement for PC games? Four years or older? I do consider GTAV to be a very modern game, although I suppose not everyone would agree. But retro? Definitely not!
Where is it reasonable to draw the line then?

And what about a "gem"?
I honestly didn't analyze the term very much when I came up with the name of the blog.
I suppose in the end it will be up to me as the author.
Most definitely really great games, and probably valuable ones as well. Interesting and unique may be covered as well, even tough they may not be the greatest of games.

For the sake of interest it would seem redundant of me to cover such well known games as Super Mario Brothers 3 for instance; everyone already know about it (don't they?).
I would appreciate your thoughts in these matters as well.

I want to apologize for being inactive for so long, and in the future I do plan to make at least one entry weekly, most likely during weekends.