There are 3 factors you have to take into account when trying to get the top spot on search.
First is time. How long have you been uploading vs the other person? In your case, you've been uploading longer. However, this is just part of the equation.
Second is the number of views. How many views are you getting vs the other person? He's got you beat cause he's getting an average of 1.5K views per video whereas you are only in the hundreds in most of your videos. YouTube sees this and combined with a larger sub count probably puts him at the top of the search.
Third is your content type. His genre is likely more searched than yours but not as saturated. While gaming is popular YT's algorithm might take into account the genre as well. Your channel has a lot of different genres and this could confuse the algorithm. While you may be a gaming channel now, at one point you had special effect videos, vlogs and even music. This all affects how YT sees your channel and thus how it shows it in searches.