If you look at the Wii it's pretty simple to see what sells on the platforms for third party.
It's either game that are different from traditional games ( EA Sports Active, Carnival Games,Guitar Hero...), games that work really well with a Wiimote ( Tiger Woods).
The only third party game that did really well and doesn't belong to those categories is the CoD:Waw and it's a port of the biggest franchise of this gen...
So if you're a developer and the game you have on the HD platforms doesn't belong to either of those categories, I don't think you would expect a port to be very successfull which is the main reason those ports are not taking place.
That and anyway we are so far in the gen now that the mahority of the fans of traditional franchise that have already had an iteration on the HD consoles have bought an HD console at this point....








