The original Spyro trilogy, hands down. I've played it and beat it over and over again ever since I was five, and to this day, i still love it and have fun. Reignited isn't bad at all, I love the graphics, but it will never hold a candle to my childhood favorites.
Pok?mon Pearl and White meant a lot to me as well, because 10-year-old me worked my butt off saving up money to get them both. I was three cents short for White, but the clerk let me buy it anyway--i could've cried, I was so happy. Pearl being my first, it paved the way to an outright love of all Pok?mon. Icy the Empoleon will be hitting 10 years old soon, and I will cherish her forever.
Magical Starsign, despite being the sequel to Magical Vacation (which was only released for the GBA in Japan), was my first ever RPG. It was difficult for me at first, but I started to get the hang of it. I lost it for three years or so, only to unexpectedly find it again and finally beat it. The art is unique, the characters are well- formed, and the story was awesome (but be prepared to get hungry, as many people and places were named after food, which I didn't realize until I was older.) It was very fulfilling, and I will gladly play it again, especially now that my brother has a copy, and we can play PVP.
On Xenoblade, my first playthrough was over 200 hours. I wanted to beat and complete everything, including beating the overpowered lv120 superboss (which involved a lot of stress, preparation, and panic on my end, but darned if I didn't do it). I still have five achievements left I'm still trying to complete.
The Kingdom Hearts series as a whole will always be a big part of my gaming life. I've loved each installment, and have tried playing them all to the fullest. Alas, my brother will forever have me beat XD
Bayonetta, I absolutely love, and am still attempting to get pure platinum ranks on every level.
It would be wrong to leave out AC Wild World and New Leaf, because they did wonders for my mental health during a bad time. I can have fun and be calm at the same time, and even share that fun and peace with others
Cool Spot on the Genesis, because it was silly and challenging all at once.
And last but not least, Mario Kart, because my whole family will play it together, and the commentary involved is hilariously legendary.