It wasn't even decent. If the best you can say is "This shit doesn't stink as much as these bigger shits" that's not much. It was junk that I'd expect from a 13 year old writing fan-fiction. It has ZERO good points. And makes even less sense. (Why did Gun attack the Ark? Was Gerald already planning to destroy the world? I thought he did that because of the Gun attack. why did he need an "ultimate" life form? and so on and so forth.)
You know what? You're right. The story for every 3D Sonic game has been bad to horrid for years until we got Secret Rings, which started putting things on the right track (light hearted, funny moments, ect).
Then we got Sonic Unleashed which stands as the best 3D Sonic story ever told. Great mix of light elements that you expect from the series while also being dark at the right moments. We also got great world building, the core Sonic cast being themselves again in a main-line installment, and some of the best production values in the series.
Black Knight is one of my favorite stories in the Sonic series personally. Every character is greatly voiced and acted, the story while one-note is decent, the character interactions were great, the usage of the King Arthur setting was good and the twist in the middle of the game was well played. Even the talking sword, something that should of been annoying, wasn't. If the game had its gameplay to be like Unleashed Day Levels, I would consider this my favorite Sonic. Everything is perfect to me here; story, presentation, art direction and even how extra characters were handled (everyone play's like Sonic but with slight differences). But the level design and gameplay drag the game into 'okay' range.
Colors was more funny and light hearted, but that was great. It was a return to the Genesis Era, something the series really needed. Eggman at his best, Sonic & Tails being great, and the tone being Sonic.
Generations had no story, so lets move on

. Lost World tried to pull what Unleashed did but due to not explaining a lot (Deadly Six, the thing Eggman had to control them, the Lost Hex, ect) and the tone being all over the place, it as only okay.
Even though Sonic Boom RoL had the story issues as Lost World (but even worse due to the games rushed nature) it nailed its tone characterization wise and the character interactions during levels (not the 'BOUNCE PAD!' 'THIS IS WHAT SPEED LOOKS LIKE' 'RIINNNGGGSSS!!!!!' quips that pop up too. many. times.) were really funny and reminded me of the cartoon (which is good, one of the better Sonic cartoons out there). Even Lyric had a decent backstory (made his suit due to being sick from interacting with the Chaos Crystals, so he hates life-forms and trusts tech due to the latter saving his life & the former almost killing him).