The original Doom 3 could easily be in the top 10 games of the last 10-or-so years. I got this primarily to play the Resurrection of Evil and Lost Missions expansion packs, which, in the case of Resurrection of Evil, I never got a chance to play on the original Xbox at the time of launch. Both were average add-ons that took less than 3 hours to plow through. Each had similar plot lines, run around the Mars base killing creatures trying to destroy or obtain certain things that had something loosely to related to how the gateway to the other dimension was opened. Of course, both end with you fighting a large demon in the alternate dimension itself. Blah, blah, blah- A fun visit down memory lane for me, but not much more.
If you have played the original Doom 3 then playing this won't be any different. There are slight differences such as brighter lights in some areas and texture changes. There is built-in multiplayer and a new level but it took me about 2 hours to complete (not rushing). Doom 1 and 2 are also on the disc but require you to NOT have the game installed in order to play them which is a bit odd. If you are looking for a completely new experience, you won't find it in this game unless you have never played Doom 3 before.