Could have sworn we had another thread like this, oh well...
My first Sonic game was Sonic the Hedgehog 1, on a bootleg CD that had about 100 Megadrive ROMs with an emulator, shops used to sell them very cheap around here, I'm not ashamed to say I never bothered to finish the game, much like the rest of the Genesis games, they seemed like any other Platformer I have played before it, then as I was scrolling the list of ROMs I discovered Sonic 3D Blast, and that was what really got me into Sonic Games, love the aesthetic and the music, I never minded any of it's control or gameplay-related issues, in fact, I didn't even know about them until years later when I found out people complained about the gameplay not being traditional Sonic-style and the slipperiness of controls.
Then as I was reading more about the game on google and youtube I stumbled upon a Gameplay video of Red Volcano Zone from SRB2, the video didn't mention the name of the game, but Thankfully some people in the comments were kind enough to give the name of the game, 3D Blast was my first true Sonic game and I wouldn't have discovered SRB2 or even got into Sonic games in the first place without it, 2D Sonic games don't interest me as much as the 3D ones, despite 3D Sonic era's poor reputation.