Correct me if I'm wrong, but according to my research, it seems that Enix was only a publisher and all of its games were made by outside developers.

For example...
Dragon Quest- The first five were developed by Chunsoft, 6 and 7 developed by Heartbeat, and 8 was developed by Level 5.
Star Ocean series- Developed by Tri-Ace.
Valkyrie Profile- Also developed by Tri-Ace.
Soul Blazer, Illusion of Gaia, and Terranigma- Developed by Quintet.
ActRaiser- Also developed by Quintet.
7th Saga- Developed by Produce.