Apparently about 700 people agree with you: https://www.ranker.com/list/ultima-games/video-game-info

The ranking they give is:

1. Ultima VII: The Black Gate

2. Ultima IV: Quest of the Avatar

3. Ultima V: Warriors of Destiny

4. Ultima VI: The False Prophet

5. Ultima VII Part Two: Serpent Isle

6. Ultima Underworld: The Stygian Abyss

7. Ultima III: Exodus

8. Ultima Underworld II: Labyrinth of Worlds

9. Ultima Online

10. Ultima I: The First Age of Darkness

and then 5 more, including Akalabeth.

I never played VII at all, but I did play II, III, and IV, and I agree with the relative rankings here.