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?

1st: Metroid Prime Trilogy (3 phenomenal single player only games in 1!)
2nd: Call of Duty 4 (phenomenal multiplayer)
3rd: Red Steel 2 (phenomenal single player with great sword/shooting combo controls)
4th: Call of Duty WaW
5th: Dead Space or Resident Evil: UC if they like rail shooters

Call of Duty 7 coming this year (i think) and The Grinder (early 2011) are 2 to look forward to :)

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...

I've played plenty of Wii fps titles. If he's looking for a fun challenge I'd recommend Medal Of Honor Heroes 2 first and foremost. The controls are tight, visuals are decent, it takes alot of skill if you choose to play on anything above green, and it has a damn fun multiplayer mode. I can't speak for other people but Red Steel was a really fun game for me. Still has some of the best visuals on the Wii and the single player campaign is worth a few trips through, no online but the 4 player split screen is a nice addition.

Call of Duty WaW is also a good game, the scale is grander then Heroes 2 and the controls are just as good. The single player is damn good and it has online multiplayer as well.

If he's looking for something cheap, awful, and would help him hate the Wii, tell about Far Cry. Grade A crap at a premium price tag.

cod4 on wii is actually pretty good

Based on your answers...Tell him to test some of this:

The Conduit has a good Multiplayer component AND is very cheap
Red Steel 2 is a great 1 player only game BUT requires Motion+
Call of Duty Modern Warfare and World at War, are good in both 1 player and Online multiplayer

Try at least 1 Onrails shooter, Dead Space Extraction its great and its cheap, or for something with a more arcade feeling House of the Dead its a good choice.

^^ If you're going to do on-rails shooter, go with Resident Evil Umbrella Chronicles or Darkside Chronicles

Red Steel (yes, the original, I loved it)
Red Steel 2 (a whole different experience from the 1st)
Conduit
Medal of Honor Heroes 2 (very good game)
Metroid Prime 3 (more adventure, but definitely worth it)
For quick pick up and play fun - (House of the Dead 2&3, Ghost Squad)

For those recommending Red Steel 2, it can be purchased with M+ included, as a bundle, yes?

Yeah, that's how I got it.