For example, a band like Joy Division. Two masterpiece albums in the form of Unknown Pleasures and Closer, and the untimely death of Ian Curtis cut it all short. They were even heading into the direction that New Order eventually went in, and it would have been interesting to see what Ian Curtis would have done if they fully made the leap into electronic music while he was still alive.
The Whitestripes
Queen
I mean sure they had so many contributions to rock, but they still had SOOO much more in them and Freddie Mercury had so much raw talent creating music he probably had at least 10 albums more in his death bed