1) Superman from Action Comics #1
2) Batman from Detective Comics #27
7) Superboy (and the LSH) from Adventure Comics #247
8) Avengers #4
9) The Brave and the Bold #28

First read in DC and Marvel Treasury Edition oversized comics

3) Spider-Man from Amazing Fantasy #15
4) Fantastic Four #1
11) X-Men #1
12) Thor from Journey Into Mystery #83

First read in ORIGINS and SON OF ORIGINS OF MARVEL COMICS books

5) Batman (new look) from Detective Comics #327
13) Supergirl from Action Comics #252
14) Captain America (origin story) from Captain America Comics #1

Not read until seeing them in MASTERWORKS and ARCHIVES

6) Green Lantern/Green Arrow #76

Had the original!

10) Avengers #16

Hmmm... Not sure, but probably in an issue of Marvel Triple Action