Since most of the time is spent out at sea the following regards graphics is the most important:
Sea and sky
U-boat and crew
Ships
Aircraft
most other graphics I don't care about really.
The other most important thing is game play realism:
sensors
tools
AI intelligence
Dynamic campaign
U-boat and ship dynamics
To me the perfect solution would have been a major graphics upgrade to SHIII with GWX!!

Yes I've said it before and is my opinion only!