Actually this isn't really the case.
A lot of people seem to completely ignore print/radio when saying something is the 'first' of something in regards to story on television. Being someone who listens to a fair bit of 40-60's radio I feel I should correct the idea Trek was setting a stage when there was science fiction shows of great quality which preceded it.
Before Trek we had, Space Patrol, Buck Rogers, Flash Gordon and many others.
And if you wanted something a little more adult you could get Journey Into Space for serial or the anthology series X Minus One, Dimension X.
And in Print you had a lot of the science fiction magazines which were all in their prime before the 1960's.
Trek didn't really set the stage for anything, it's just the largest example and that's why it'll inevitably draw a comparison to any other space show.
Plus anyway we'd say Trek ripped off Wagon Train & Voyage Of The Scarlett Queen.