Rise of the Triad was originally slated to be a sequel to the well known Wolfenstein 3D- a fact that is evident based on the soldiers and MP40 sub machine gun that is still present in the game; the Wolf3D engine was enhanced to a point where it is no longer distinguishable in comparison to Wolfenstein 3D, but that doesn't really contribute to the game's entertainment value. Minds were changed- this game was not meant to be a sequel for Wolf3D- so, instead of being a Nazi killing fest, the plot was instead reworked into telling the stories of several characters in a organization known as H.U.N.T, who are sent to investigate suspicious activities on San Nicolas Island. They are met with hostility as their boat is destroyed, forcing them to fight their way out, while stopping the cult at the same time.
ROTT has an atmosphere that is similar to Arcade and Platformers from the Apogee catalog- moving platforms, discrete traps placed in (somewhat) hidden locations, including numerous powerups and obstacles: a recognizable trait inserted into a lot of old-school FPS's- however, it doesn't pack the same punch as other memorable and well designed titles of the 90's.
Level design in ROTT is nearly as interesting as its color palette (several shades of brown and gray, hooray), and the weapons are decent, but not anything incredibly memorable and interesting, which is important for this genre. Aside from this, some technical aspects are notable, including bullet holes, fog, panoramic skies and the like, but is also shackled from earlier limits set by the Wolf3D engine.
In other words, you may find that you appreciate the old school charm that ROTT has- but this is really a taste that varies from person to person. As for me, my time will be spent elsewhere. Unless you REALLY love potted plants.