It's interesting how much X-Men 1 seems to fluctuate for people (anywhere from 4 to 9). I understand that its Silver Age impact (at that time) was not as significant, but its effect on the Marvel universe, not to mention dominance of the bronze age (IH 181, GSXM 1, X-Men 94) in my opinion makes it easily the 4th biggest silver-age key - hell I could even put it at number 2. I would be interested to hear why people think a book like TOS 39 or JIM 83 are more important than X-Men 1, as it seems both TOS 39 and JIM 83 only get a bump because of recent movie success.
I also don't get TTA 27 being in the top 10 over something like ASM #1 - but that is just my opinion. I get the appeal for Antman, but he was just never a major character.
It is interesting to see everyone's thoughts though.