I would recommend Trauma Center: Second Opinion. It makes good use of the Wii controller, and it's not a straight port of the DS version. There are 3 selectable difficulty settings for each operation scenario. Normal is the equivalent difficulty of the the DS version, which was considered pretty challenging.
Metal Slug Anthology is ok for having 7 games packed in, but the strange control configurations are a big turn-off for some. The game does not support the Wii Classic Controller. You can ues a Gamecube controller, but it doesn't support the D-pad; you have to use the analog stick.