On the technical side, the biggest productivity gain is from having a garbage collector. Beyond that, language features: while C# 1.0 started in a spot very similar to Delphi (+GC), it evolved much faster - e.g. getting generics in 2005.
But, yes, if you looked at it in 1.x days, it really looked a lot like Delphi libraries with Java-like syntax. So if you were already using Delphi, there wasn't much point.