Like when people hear something new and they LOVE it and might say something like: Good God! WHAT is that? Which decade...according to you...did that happen the most?
60's and early 70's.
The mid to late 70s for me. 1977 in particular had some of my favorite artists' debut albums:
And other notables debuts:
The Sex Pistols
Peter Gabriel and Björk also came out with the debut solo albums.
50's through the 70's.