Myth 3 is the weakest of the unique and innovative Myth series. It manages to capture the dark, bleak tone of the fantasy world, and pack in plenty of mission variety in the campaign just like previous games. The tactical combat is still delightfully brutal, gory, and frantic. There is a much-expanded roster of units with unique abilities.
However, the translation of units from 2D sprites to 3D models loses some of the charm. But most significant is the rushed development schedule that left an unpolished campaign with frustrating difficulty spikes and one or two buggy missions that can only be completed by exploiting flaws in the enemy AI. Myth 3 clearly needed more time in the oven.
A more fundamental but more subjective flaw is the narrative: Where The Fallen Lords works as a small-scale tactics game of a rag-tag group of desperate auxiliary troops doing small guerilla missions against a vast army of darkness (with epic events alluded to concurrently or historically), Myth 3 attempts to depict these epic events in-game - The problem is the Myth engine and gameplay are only intended for small-scale tactics (so the "vast battle of the trow" is apparently just 12 humans against 5 trow?). Depicting it in-game strips away all the mystique of the lore teased in the previous games, while adding few (if any) of its own little allusions to vast depths of lore. Where The Fallen Lords felt like a small glimpse of a much larger, deeper picture, Myth 3 feels like it just tries to show you the whole picture. Thus, in attempting to flesh out the lore of Myth, it ends up flattening it out into a simple 2D picture and feels a little underwhelming.
Certainly flawed, Myth 3 is still more Myth. It fits right in with the series in terms of gameplay style and tone of the world. It provides more morsels for a very hungry fanbase.