Nowadays it's hard to sell it I guess. But lets try: You can always control the direction of the ball/sonic like in any jump n run. The levels are actual worlds, not just a flipper table. So there are real switches, sewer pipes and gates hindering your progress. And each of the 3 gems can be hidden like a riddle in the world, where you have to think how to reach it. Each level has a unique, weird and fitting boss. And after each level except the last there is a unique bonus game. And there are alot of unique gameplay elements combining jump n run and pinball. I never finished it and stage 3 is a bit boring due to the level sprites (purple computer machine...). And finally the sounds and music are pretty good.
If you are more into pinball than jump n run, I recommend devils crush.