Not quite as great as Dimension of the Machine, but still an improvement on the base game. Corpse Run and Darkest Depths are especially awesome designs with good environmental storytelling. The last boss is frustratingly difficult but I honestly love the way it (spoiler alert, I suppose) incorporated enemies from Quake 1 to tie the Q1 and Q2 stories together. Not 100% sure the explanation they settled on makes the most sense, but it feels right.

Final Quake 1/2 rankings:

1. Q1: Dimension of the Machine
2. Q1 (base game)
3. Q2: Call of the Machine
4. Q2 (base game)
5. Q1: Dimension of the Past
6. Q2: The Reckoning
7. Q1: Scourge of Armagon
8. Q1: Dissolution of Eternity
9. Q2: Ground Zero