One major milestone was the creation of Superman in 1938. It launched the superhero genre which became a dominant force in comic novels. Another milestone was the introduction of manga to the Western world. It broadened the global perspective of comic novels. Also, the rise of graphic novels as a legitimate literary form in the 1980s was significant.
It depends on your taste. If you like superhero comics with complex characters and exciting plots, then you'll likely think it's good. The world-building and character development are quite impressive.
The Invincible comic has indeed come to an end. The story reached its conclusion after a successful run. Fans have had to say goodbye to this beloved series.