It got some things right; threading (even ten years on Java has a more reliable thread model than tcl/perl/python/ruby), strong typing (not much use day-to-day, but incredibly valuable for building extensible libraries that can nevertheless be evolved without breaking existing code), maven.

I think it achieved the enormous success it has mostly by being a conservative, incremental improvement over C++ and Cobol. A lot of things introduced in later versions of java were things other languages had been doing for years, but an unwillingness to adopt unproven techniques is the best thing about java. I don't think it even is the best choice for any given problem - it's just that in a real world of mediocrity and turnover, java makes it possible to produce reliable, boring code with minimal risk.