Sonic Blast is by no means a terrible game, but is also definitely a mixed bag when it comes to quality.
Released for the Game Gear as a more traditionally-designed alternative to the Genesis' Sonic 3D Blast, Sonic Blast is, conceptually, a pretty standard affair as far as the series goes. The game revolves around the playable characters of Sonic and Knuckles as they try to collect the Chaos Emeralds via platforming levels and special stages.
The game's level design was on par, the music was fine, and pre-rendered graphics made it look fairly advanced during the time of its 1996 release.
That said, the graphic style of the game is sure to be divisive among players, especially given how it's aged. Plus, the controls aren't nearly as tight as some other Sonic titles and the amount of space that character sprites take up has been a big hangup critics have had with the game. And while that aspect is more of a nitpick than anything else, it can still be rather distracting.