I always felt like the excitement came from the difficulty and my own precision. Conquering the math, the situation, the weather, the technology.
Of course, I play manual targeting. I too got bored sinking merchants when it was simply a matter of point and click and a guaranteed explosion.
Without manual targeting I wouldn't have a whole lot to put my energy into. Maybe role playing I guess.
Course I'm one of those weirdos that plays Arma2 heavily modded with my friends, and rolls around a middle eastern map patrolling in humvees, stopping in towns, checking buildings, and not finding any enemies for 45 minutes straight and still find it fun. Its the same as SH3/4 though in that after 45 dry minutes if you've let your guard down suddenly your opportunity shows itself and you can either react in a way that wins, or mess it up.
That said, a good task force always spices up a dreary patrol. Nothing gets the blood pumping like a 25 knot target that you only get one (manually targeted) shot at.
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