So even if you'd recorded it during first broadcast, the Blu-Ray versions would show more detail?
If it was broadcast at 720p (or 1080i?), then you'll get a resolution increase on Blu-ray. You'll also not have so much compression that broadcast video has to go through. So, yeah, it will look nicer. Maybe not loads nicer but, short of remastering, that's about as good as Enterprise will ever look.
They're on iTunes in HD as well, aren't they? That's probably a closer comparison.