Wii is actually getting a lot of third party support as of now- see Scarface, The Godfather, Manhunt and Medal of Honour: Heroes 2 for games that due to Wii control and are much better than their Sony and Microsoft counterparts. I really think that the whole "Wii is for casual gamers thing" is untrue: Certainly, there are a lot of "casual" games on the Wii, but there are also a lot of exclusive"hardcore gamer" games that are also very good- see Battalion Wars II if you enjoy strategy, the new Fire Emblem game for RPGs, Mario, Zelda, Metroid, SSX Blur, Excite Truck, Resident Evil: Umbrella Chronicles, etc... The main attractions of any newer Nintendo system are going to be Mario, Zelda, Metroid and Smash Bros; that being said, if you look beyond those, you'll find a lot of good exclusives and third party games for the Wii; add to that the Virtual Console, a good online system and that the Wii is 100% backwards compatible with all Gamecube games (unlike, say, the PS3), and I'd say its worth getting.
Not to say there's anything wrong with buying another system (though I do have a lot of doubts about the PS3 and have not been impressed with it thus far): The XBox 360 has a fantastic lineup of games, and the best online play of the three. Just wanted to point out that the Wii is a viable choice for the "hardcore gamer" (though I do hate the term with a passion).
