Wow! I'm loving the feedback from all directions. Its nice to have a nice, intelligent thread that hasn't gone up in flames! Now for my 2 cents:
For those wanting a a GTA-esque game, you're in luck. True Crime: Streets of L.A is slated to come out on all three platforms. Worst case scenerio is that its a GTA type clone (Hardly, since it boasts some features such as an intricate hand-to hand combat system, GTA was mainly about your gun or occasional baseball bat.) Its coming out in Novemember, so unless they pull gamecube support at the 11th hour, your wish will come true. Now all that needs to happen is for GCN users out there to show that truly want these types of games on Nintendo's system when it comes. If not, publishers will be proved right, and will go elsewhere. Take that for what you will.
If I'm not mistaken, Rockstar(and subsideries) have avoided nintendo like the plague. The exceptions are Smugglers Run and Conflict Desert Storm. Whereas even the most stubborn publisher may have gone to the GBA, Rockstar has gone on record saying "GBA does not suit our needs." So if they go portable with N-Gage, PSP or some other contender, they might have the power to stick it to Nintendo in its most profitable area. They just bought out TDK interactive, saying it will delve into 'younger demographics' and with Rockstars money, it sounds like they really, really want to wipe Nintendo off the face of the earth.
I'm not going to say what Nintendo needs and need not do: I'm just somebody with too much time on my hands! Though I will say that more Exclusive Mature titles wouldn't hurt now would it? And while I'm at it, an official Nintendo mag geared for the 18 and up crowd. Doesn't have to be trashy, maybe something like good ol PGC

I'm done now. Thanks for listening and keep those ideas running!