But they do replace the originals - the originals aren't for sale anywhere but on disc from eBay and Amazon resellers with old stock. And LucasArts isn't likely to rerelease them on Steam or elsewhere, either, because they know it would cannibalize their Special Edition sales.
Don't get me wrong, the ME2 special edition fixed most of my complaints about the first one, and I lined up to buy it like the slavering dog that I am. But I still just want to see a legit, digitally distributed version of the classic LucasArts games. They already did it with a bunch of them, so I don't really understand what the hold-up is.