I finished Resurrection of Evil for the first time. I quite enjoyed it, it goes for a more action-oriented approach than the base game and is also somewhat more challenging to boot. I actually died more in RoE than I did in Doom 3. The new toys the game gives you such as the Super Shotgun are also pretty sweet, though the Grabber can be occasionally broken (it's insane how fast it kills Hell Knights). It's also got a more satisfying ending than Doom 3 (and by that I mean you get an actual fucking boss fight with the antagonist and not just toss a superweapon at a giant monster 3 times). On the whole, it's Doom 3 without the fat, which is probably why I think it may be more fun than the original.
RoE showed greater potential in Doom 3's approach to the series, and that's why I'm a little sad we may never see that again. Don't get me wrong, Doom 2016 is probably the best thing to happen to the series and perhaps this gaming generation, but there is something to how Doom 3 was a more horror-focused. slow paced affair in stark contrast to the rest of the series.