It has to be said that DOOM still remains at the top of the list for the best games of all time even today.
Compared to the shooters out there today it can easily be said that DOOM is outdated (actually that would be the biggest understatement of all time). But, DOOM still is better than the majority of games out there today and more fun can be had playing it then most of today's FPSes. The single players first three episodes are full of action against enemies that still are cool, scary, and fun to fight against. The levels are designed so that they are mentally challenging while at the same time having not too many true puzzles.
Depending on your mode of play the game is either of average difficulty or next to impossible which adds tons of replay value as well.
The best part of the game, however, is the multiplayer. If you have access to a LAN then you likely will loose many hours, or weekends, in deathmatches, or even in cooperative play through the main campaign. Both easily beat out even many of today's most fun multiplayer games.
The extra episode thrown in for this version is the only stain on this game. It is full of poorly designed levels and clearly is just a rush job made to get another DOOM on the market. There is no new boss at the end as well you just replay the one from DOOM's episode 3.
The graphics are outdated of course but the sound is still used in movies and video games today.
It has to be said that DOOM still remains at the top of the list for the best games of all time (PC or console) and The Ultimate DOOM is a great buy for fans of videogames in general. Pick it up in the Collector's Edition ASAP.