He wants to play alone?, or is online multiplayer necesary?
The Conduit has a good Multiplayer component.
Red Steel 2 is a great 1 player only game.
Metroid Prime 3 Corruption or Trilogy are First Person Adventures and great games.
Call of Duty Modern Warfare and World at War, are good in both 1 player and multiplayer.
Resident Evil Umbrella Chronicles and Darkside Chronicles are On-rails shooters.
Give us more info so we can make better suggestions. Does he have multiple consoles, or only Wii?, you know of some games he already has? Does he cares if the games are onrails?
He didn't give me a lot of details about what he was looking for, but I do know this much.
He only owns a a Wii. He does enjoy playing games online (example: we both play UNO online via Wii, and he likes that), so presumably an online component would be good. Also, he just recently purchased the Wii (couple months ago - thanks tax refunds!), so he only has a couple games, like NSMBWii, Wii Sports, and I think Wii Play. Also, he lives alone and works really odd/varying shifts/hours, so I think a solid single-player experience would be key for him. I do not know of any prior consoles he owned, so details beyond that are kind of sparse. I will have to ask him for more specifics...