I think DT's lyrics were far better and more notable early in their career (not just because Kevin Moore was there, but JP was more consistent back then, and even Portnoy had a few good ones), but This Is the Life is definitely a standout.
Favorites lyrically would be Learning to Live, Voices, Surrounded, Space Dye Vest, Pull Me Under, Lifting Shadows Off a Dream, Take Away My Pain and A Change of Seasons.