My happiest days were watching my children being born.
There have been many other happy days, most of them revolving around my wife and kids.
Papa was really happy about two weeks ago when his baby girl walked to receive her master's degree in a scientific field, then had to return to her job, making more money than mom and dad combined.
Being truely happy, comes from the inside. Toys and accomplishments can make you dang happy for a short time, but those things fade rapidly.
There is an old story of a Monk and his apprentice, planting a garden. The apprentice asked the Monk what he would do if he knew the world would end tomorrow.
The Monk replied, "I would finish planting the garden." That is happiness