Survival and Skywars are my top 2. I do not really play on the others much. Survival may be my #1 though and the staff is the BEST pyrolily was right.
Skyblock of course! You start on a 10x10 piece of floating land, with nothing but a few basic tools. From there you complete challenges and build to make your island the best of the best, trying not to fall to your death in the void throughout your journey. The challenge and competition are awesome! Well I am on Skyblock so that should be the only reason you need