Appart from the already mentioned MKWii, SSBB, NSMBWii; and for the Wii series games like Wii Sport Resort or Wii Party. You should look into Big Brain Academy multi; or the Mario & Sonic olympic games, which has some frantic mini games.
But one that get's rarely mention is the Trauma Center series, and it's one I always look forward too to play with someone (Trauma Team is taking too long...), both New Blood and Trauma Team have coop.
And lastly for music games, both Just Dance or We Cheer series' are nice to move along, but for cheap you can get Samba de Amigo which also does a pretty good job.







