Aces and SH1 have the limitations of their days, but other than that they were, and still are fairly solid games. I was really surprised how good SH1 still is, sometimes you tend to embelish your old memories, but this game is really good.
The prob with SH3 and 4 (besides my opinion on gameplay flaws
) is that they completely missed some obvious features, and those aren't in any way limited by the tech available.
One of the obvious, the land that "doesn't exist". Sail just north of Scapa, hidden by the island, and the battleships in the harbour will open up on you. Sit on the bottom (need mod for that) and enemy DDs can pick you up without problem. It can't get more basic than that for a sub game, and it's absent. When you read that wolfpacks barely made it in game but that the exterior sub model has 1 million polygons, well it's clear that the focus isn't quite the same as the old sims.
If a small indie dev made a loose remake of SH1/AOD with all the good old features + the good new features (hydrophone, TDC tools, crew management) with low-tech (cheap and quick) but crispy graphics, I'm sure simmers would buy it.