I rather they make remakes and reimaginations of games that have yet seen a rerelease yet. Sure I would like to be able to play as many of my old favorites on the switch as possible, since it is my favorite system, but well received games that is currently locked on a specific system is what I mostly would like. Previously named Mario Sunshine and Eternal Darkness come tom mind as well as Paper Mario TTYD.
I think that Mario Sunshine get my vote. It is stuck on the Gamecube and compared to many other main-line Mario games it is not regarded as a masterpiece. I think they could fix it up and give a new generation the chance to play it.
Even if reimagination of old favorites on NES, SNES or N64 would be neat, at least it is possible to play the games in some form on modern systems. That is why the focus land on the oldest system yet to have any digital rerelease of the games, the GameCube.