Retro gaming for me means good memories and occasionally playing a few of them where the frustration factor has aged well
Retro games, all categories (except early arcade hall games) have a vast majority of games that frustrated even 15yos with lightning reflexes! The reason we put up with the frustration was to see another screenful of awesome (back then) graphics.
Now, the graphics don't look awesome to most of the population, and so there is less incentive, especially for some games that require you to play flawlessly to even survive. Gaming concepts have also moved away from the simple "levels" and "shoot everything" - at least the games I enjoy now.
Multiplayer gaming in whatever form has always worked and will always work, because it addresses the competitiveness in most of us and not the game "mechanics".
There is also the retro style, which will be strong for the foreseeable future. There is something cozy and camp about loading up a simple old game and get into it BECAUSE you enjoy the hand-pixeled graphics more than say, a vacuous sports game with ever so polished 3D graphics with effects. The retro style is even something people admire as a form of art expression and try to emulate and incorporate into modern works. (EDGE on Steam and Minecraft are good examples.)
There. Essay done. Hehe