It is not fair to judge a coaster such as Space Mountain to a giga such as Steel Dragon. Both are different rides and give different experiences. Thrill coasters, on one hand, are about speed and intensity. Themed coasters, on the other hand, are about immersion and telling a story. This is why Disney rides have a reputation for being the best themed in the world. Take Radiator Springs Racers for example. That ride aims to authentically re-create the world of the Cars films through its theming and landscaping and immerse guests in that world and tell a story through animatronics, music and special effects. On the other hand, a thrill coaster such as Fury aims to go fast and give its riders an intense ride, without immersing them in a world or telling guests a story. Many thrill coasters (TOT2, Buzzsaw and Cyclone in its heyday) have tried to use both, but have done one or the other extremely poorly (typically theming).
For me, personally, I like rides that have used a combination of both elements with great success, and good examples of this is Hulk, Space Mountain Mission 2, Rock N Roller Coaster and Expedition Everest. All four of these are obviously intended to be thrill rides, however each of them also have a theme that makes sense and immerses guests in a specific environment.