No better forum on PPRuNe for this sort of thing
Database development is probably a lot more interesting in the small business world, because you'll get to do everthing from gathering requirements and design to roll-out and support. However, small businesses don't seem to have much of an IT budget, so unless you can find a particular niche you probably aren't going to make yourself rich. There's more money in Enterprise development, but in that world databases are rather dull abstract things; in J2EE (which is what I know) they're an XA resource hidden behind JDBC or, increasingly, an Entity EJB, and then - by architectural design - you hardly know it's a database at all. All of the clever stuff that might interest you is hidden in the EJB container, so it's probably not the best job if databases are your thing.
Have you thought about getting some database administration experience? Oracle DBAs or their DB2 equivalents don't seem to do too badly for themselves, and they usually seem to get to play some part in application design and architecture, even if they don't have a real development (i.e. code-writing) role.