I think the only reasonable place to put Doom 3 is before all the other games:
- Doom 1's manual makes it clear that there are other marines working on Phobos and Deimos, as referenced in GermanPeter's recent series interpreting the levels:
https://www.youtube.com/watch?v=VqWT8h-crjQ - The teleporter technology and technological investment in Hell is much further along in Doom 1 than in Doom 3: the teleporters are brand new secret projects in Delta Labs in Doom 3, but by the start of Doom 1, they've got several facilities working on them and the entirety of Deimos (
https://www.youtube.com/watch?v=qRKaJkzRZ50) has been teleported to Hell, where it serves as the setting of Episode 2.
- The events of Doom 3 and its expansion could be covered up. The loss of containment and invasion of Earth in Doom 2 (
https://www.youtube.com/watch?v=kxlulRRVsPc) are much more extreme and would probably spell doom (heh) for Betruger's funding opportunities.
It's not a perfect timeline—for example, Doom 2016 has a UAC logo much closer to the one from Doom 3, but the overall sequence of events works better if we regard Doom 3 as a prequel. There's even a narrative "match cut (
https://en.wikipedia.org/wiki/Match_cut)": Doom 3 wraps up with more marines being sent in to perform cleanup, and Doom 1 opens with a massacred team of marine cleaners...
IGN's description of Doom 3 doesn't really make a whole lot of sense; they sort of just dismiss the game entirely as not being part of the continuity at all. In the end, all they did was sort the games by release date!