Hi F1motion.
I've played all Silent Hunter versions, and yes, when Silent Hunter 5 appeared it was marvelous to look at, and being able to move around inside the entire sub an awesome experience. However, the game bugs and even new gameplay mechanics and designs made the game a lot less fun to play than its predecessors.
The good news is that thanks to the modding community, with the Wolves of Steel mod for Silent Hunter 5, a lot of the gameplay glory that was apparent in Silent Hunter 3 & 4 has been returned to the game. I would definitely recommend you to go with Silent Hunter 5 + The Wolves of Steel megamod. I am almost certain you will not be disappointed.

And welcome abord!