The Classic Series was a range bought out by Nintendo Of Europe (NOE) that was sold though out Germany, France and the Netherlands between 1993/94. The Classic Series was nothing more than repackaged existing Nintendo developed titles. The new box and label art was mostly recycled Famicom art.

Mario Bros is the only game in the Classic Series that is different from its original release.
The speed of the game was improved along with the graphics making it a lot more like the arcade version it was ported from.

The following games were released under the Classic Series line.
Ice Hockey, Mario Bros, Pinball, Soccer, Super Mario Bros 3, Tennis, The Legends of Zelda and The Adventure of Link.

The Classic Series was not out for long and being limited to only a few countries in Europe the games are quite hard to find today. As for the exact rarity of each game I do not know but I would say that it is defiantly worth picking up Zelda 1, Zelda 2 and Mario Bros.

It has recently come to my attention that the Game Boy also got the Classic Series treatment as you can see here.