Is this really the first time this has been scanned? I think I must have seen this cover so often in in-house ads of other Game Player's mags that I convinced myself that I already had a copy, but it appears that I don't.😆 I'm positive I saw this on newsstands at the same time as Game Player's Strategy Guide to Nintendo Games Vol.1 No.2, which there are two covers for - one with and one without the triangular contest blurb seen on this cover. I'm pretty sure both of these issues (and possibly others) received multiple printings, making pinpointing their exact release dates difficult.
One of the covers of issue 2 (which Retromags lists with an "August 1988" date, the same as this Buyer's Guide) features the same contest blurb as this one but displays a "sell until May 16, 1989" note, suggesting that this Buyer's Guide issue was likely published sometime in 1989 as opposed to "August 1988" as listed here.
At any rate, it's almost 100% definite that the dates listed at Retromags are incorrect, unless there was indeed a one year gap between issue 3 (September 1988) and 4 (Aug-Sep 1989). 😂
Relevant for this thread, I found Gamest Issue #125 and uploaded it to archive. This issue came with a poster which I don't believe is scanned. I believe this is a regular issue of Gamest much in the same way the previous SFII issue was dedicated to one game. I think later one they spun these issues off into the "Gamest Mook" line. If you check archive there's other issues of Gamest and Gamest mook floating around archive.