I'm not much into ports of old games at all, except for decent remasters but i'd have a few.
Fallout 3/Fallout New Vegas: They should be portable very good and could have enhanced graphics over the console versions
F-Zero GX HD, old but i'd either love a real remaster or a new F-Zero that goes in the same direction.
Mass Effect Trilogy. I still love Mass Effect. Especially the first game. Maybe some more diverse buildings and ships for all the side missions and improved combat, because there's room for imoprovements.
Star Fox Zero: Honestly, this one would need to be redone from scratch. Keep scenarios and most of the basic layouts but with controls worthy for a Star Fox game, good graphics and online coop. Replace the slow robot parts that ruined the pace with new areas. And bring back the music of the original SNES game.
Witcher and Witcher 2: I don't believe that Witcher 3 is portable to Switch, but the first two should be. And the first Witcher never made it to consoles.
And yes, please do:
Vanquish. Great third person shooter SEGA seems to have no interest in. A sequel would be better of course, but i'd be fine if we got a port. It's a shame Vanquish isn't even backwards compatible on Xbox One.