Oracle RAC and Informix. The single reason for moving off Oracle was the hard limit of four servers in a RAC and the degradation of performance at that. Meaning Oracle really is not scalable across servers, but requires massive increase in individual server specs.

Oracle and Informix are more costly deployments and support models, from a pure licensing perspective.

The products we used most before Postgres were Enterprise database products. Of course, we are still using Enterprise database products, but we started using Postgres because it was cheaper and it could do what we needed it to in certain applications.