I saw my first Dead concert in 1977 (Palladium in NYC) and was lucky enough to see them and the Jerry Garcia Band over 100 times. To me, Jerry had a unique guitar sound that has been rarely duplicated. When you hear it out of context, you know it's Garcia. (The same can be said of Neil Young, Pete Townshend, John McLaughlin, and other icons).
The Dead also instilled in me a life-long appreciation and love of live music in many forms, but IMO, the Dead set the high-water mark for rock music performance. No two shows were ever the same, and they let the music be the primary focus. I really miss the Grateful Dead!