The Classic Doom games are some of the greatest first-person shooters ever made.
Quake is considered a classic and rightfully so. It’s only disappointing to know the series would become very inconsistent with sequels that share no real relation to the original game other than the Quake name.
Tyrian 2000 is a shoot-em-up packed with content and diversity. It never gets stale and is always throwing something new at you which always keeps it interesting.