Sonic Adventure & Sonic adventure 2: Arguably two of the best Sonic games to date originating from the Dreamcast they made it all the way up to Gamecube, ps3, xbox 360, ps4, xbox one, and PC, and would be a welcome addition to the switches library!

Great reasons why the would be perfect for the switch:

These are the Sonic games that molded a generation of Sonic fans. A switch port would allow a new generation to experience a great part of Sonic's history and allow those who look back positively on this game to take it with them on the go.  . Plus the opportunity to raise chaos at a moment's notice is probably the best conceivable bonus of these ports. In addition the local communication that the Nintendo switch provides also adds an extra layer of unique opportunity to these ports. Imagine battling someone in local battle mode or trading chaos with your friend on the go.  

With most modern Sonic games focusing more on either the boost formula or the classic formula it seems that Sega hasn't really given adventure formula fans the content they desire, this would be a way to satisfy the long time forgotten or overlooked third part of the Sonic fanbase.