Came across oldgames.sk, which helpfully allows you to search for games by magazine and takes you right to the page it was reviewed on.
M1 review, Excalibur #52
M2 review, Score #41 (only 3 out of 10?!)
M2 review, Level #22
And the M2 demo installation screen from Score #33's demo disc.
So the German magazine reviews I was shown ages ago weren't too enthused, and at least two of the above weren't, either...feels like Marathon just didn't really catch on in Europe. :/ There don't seem to be any reviews for Infinity.