[jonathanstrange]

I was never more productive than with REALBasic, it was a true RAD tool, and I'd happily use Xojo nowadays if it wasn't so expensive. That's a "modern" structured BASIC so I guess not what you had in mind.

One thing I've learned over the years is that the language is almost irrelevant, the tooling and 3rd-party library support are much more important.