Quite a few games you can just download on your Wii.

Super Metroid, A link to the Past, Super Mario World, Chrono Trigger, and FF 3 are games everyone should have though.

The first 3 you can get on Wii for sure.

As for the Trigger/Cross argument, both are excellent games. I think I prefer the Trigger storyline, Cross has a more customizable battle system and a hell of a lot more characters to choose from though so that is nice also.