As of the Enhanced Edition of the second, I think you could come by just fine without the 1st game - the second now comes with some background explanation videos on Witchers, the plot of the first game etc. If you want the detailed experience, you should still play the first game, but the second game does a fine enough job at (re)introducing the player to the world and characters to get by with it as your first game.
The Enhanced Edition of The Witcher 2 comes with this video summary of the first game, specifically:
It does not include the sidequests or anything, but does very well in summarizing the main storyline. As I said, if you want the full depth, read the journals etc, you'll still have to play the first, but there have been little complaints about not understanding the story from just playing the second.
And, for good measure, here's another included video about Witchers in general: