Sonic the Hedgehog is probably the video game franchise closest to my hearts, my childhood will always be defined by Dragon Ball Z but Sonic the Hedgehog is an easy second place, which is fitting, since it lifts so much from Dragon Ball Z anyway. I've played Sonic the Hedgehog 2 so many times growing up, it was basically the game of my childhood. And I'm the younger sibling, so I was always Tails which meant I spent a lot of time not playing the game as Sonic got the speed boost and left for dead, but hey, I was a big help with boss battles. I'm not as thrilled with the first game in the series now, I still like it but it has Labyrinth Zone and that's a crime that can never be forgiven, but the other mainline Genesis games are something I still hold with a great fondness. Also played a lot of Dr. Robotnik's Mean Bean Machine, so much so that in Sonic Mania when the boss battle of Chemical Plant Zone act 2 was a match of Dr. Robotnik's Mean Bean Machine, I almost cried from the nostalgia. Sonic Mania is probably my favorite Sonic game as a whole, it's just fantastic on so many levels. Multiple different characters with unique play-styles which can even serve as basically a difficulty setting, every single Act has a unique gimmick to them, keeping the gameplay consistently fresh, Tee Lopes makes love to my ears with fantastic remixes of old classics and new compositions, the game is drenched with the wholesome kind of Sonic fanservice, Encore mode is seriously cool way to re-experience the main campaign, and I think it has the best boss fights in any platformer I've played.
But even though I love the classic style of Sonic games, I am actually a fan of several of their games following the transition to 3D. I love the Adventure games, and yeah, I have loads of problems with both of them, but I might've spent more time with Sonic Adventure 2 Battle than any other Sonic game because the Chao garden was awesome, and allowed me to play the few levels I found really fun and ignore the abomination that were Knuckles & Rogue's levels (which is doubly bad because in Sonic Adventure 1, I love the Treasure Hunter levels, but they made baffling changes to them in 2). However, then there's Generations, which is easily the strongest 3D Sonic game in my opinion. I'm a little biased, considering it was the first game I ever platinum'd but it was awesome to revisit iconic stages throughout Sonic's history in both the modern style and the classic style, especially since the modern style was really well designed here (unlike in say Forces), with multiple branching paths like you'd find in the Classic style (which while not a perfect replication, was still a blast to revisit). Sonic Mania's Chemical Plant Zone Act 2 is my favorite Sonic level for the Classic style of gameplay, and Generations Rooftop Run is my favorite Sonic level for the modern boost style.
So yeah, Sonic has provided some of my favorite gaming memories over the years, and it's one of my favorite video game franchises out there, just not my favorite due to the amount of awful games they've released.