What part is hard? :6
Some people have difficulties reaching Pro status in certain sports. Titles such as
Wii Sports require a lot of motion-handling, and it's not always easy to master a video game sport when one doesn't practice enough, or finds harder opponents too skillful to beat. It's similar to real-live sporting situations.
I also believe that the boxing sport is kinda glitchy: The controls are not always smooth in response apparently, and does not emulate hand-movements properly.
I find all games easy, but Wii Sports is the hardest.
If
Wii Sports is hard, then you should try out
Wii Sports Resort! You won't believe how much trickier true 1:1 motion is and is too much to handle!