You'll get more out of the games for certain. But no.
Usually I'm a stickler on finishing the first games in a series, before moving on.
That said, I played the hell out of the W1, loved it, but got stuck in the swamps, took a break, came back much later, couldn't do it. So then I gave in and watched the rest on youtube. (Summary).
With the Witcher 2, I tried a couple times, didn't get very far. Then before wild Hunt, I powered through and played it on Easy. That said, before I knew it I was enjoying myself, and felt as I rushed it too much. Great game.
Wild Hunt is a on a whole different level. It is in the top five if not THE best game I've ever played. It's just so close to perfect it's hard to believe.