Not sure I agree with the premise. Plenty of A-list talent was wasted on cardboard cutout characters in the prequels: Liam Neeson, Ewan McGregor, Natalie Portman. Samuel L Jackson was just another one.
I'm going to go with "No, he was not a good addition", but that's really no reflection on him given his company. Unless I hear a rumor that during shooting, he grabbed a movie camera, threw it on the ground, and pooped on it, in which case he was a great addition.