I haven't touched any of these HD collections, but I do like the recent ports of Sega games on XBLA - Virtua Fighter 2, NiGHTS Guardian Heroes, Radiant Silvergun, etc - I'm generally very happy with these because the changes are appreciable but not so extreme that you lose the original game (and you can often make them almost exactly like the originals anyway).
The one I'd really like to see is Final Fantasy XII, I think that would look amazing done up <3