Wii Sports and Gears of War both deserve an honourable mention in my opinion.
Gears was visually mindblowing at the time and was really nailed third person cover shooting mechanics to the point where its DNA is still strong in most modern TPS games. From its crunchy combat, to its gritty visuals, to its moody atmosphere, it set the tone for much of the generation that would follow. An iconic game that changed the medium forever.
Wii Sports was also really special. The way it brought together gamers from all walks of life was magical; my memories of playing it with my Mum and Stepdad, who'd never been able to get into gaming before, are some of the warmest of that time of my life, finally getting to share in my favourite hobby with my family.
It was also one of those moments that felt like a leap into the future; playing with motion controls for the first time felt like something straight out of Star Trek, and the sheer kinetic joy was incredible.