There are some interesting viewpoints floating around here, especially the one of the original poster.
I'm not technically savvy like kenn is but at least I have a basic understanding of computer terms. One thing I've noticed with computers is that it doesn't matter how fast the CPU is, the computer will never be fast unless it balances everything inside it with the CPU. And that's what Nintendo has done with its consoles. Slower clock speed CPUs and then balance out with the rest of the system through Graphics card, bus speed, RAM etc. The gamecube, as a result is almost as good as the XBOX and is a very energy efficient machine in comparision to the XBOX.
Sony and Microsoft have never opted for that approach because their philosophy is 'the bigger, the better', which is flawed. You can have a game system or a computer that gives out the best possible graphics of its time but in a few years down the track it's likely to fail due to overheating problems and flaws within the design of components and how they work with each other. That is often the problem with XBOX and PS consoles - they overheat too much and every now and then, a problem crops up with the system integrity.
What nintendo has done is virtually work in the opposite direction of Sony and Microsoft. I'm sure they did think of improving their graphical prowess of the Wii back in development stages. But they realised that if they took that path, focusing on graphics and nil gameplay, they would not get anywhere in the long term and the industry would stifle. Instead, they focused on minimising power consumption by decreasing the size of the components involved and using tried and tested methods of using the most efficient technology at the time. Hence the price cost is cheaper, the size of the console is very small and has minimal heating problems.
In terms of playability and gameplay, the Wii has alot of potential there. But its up to the developers to fully utilise the uniqueness of the Wii console. The Wii alone cannot win without having a good developer backing behind it. That is what enabled the PS2 to win the current generation war. It had alot of games but very few of them were good games.
Grahically, the Wii is mediocre and I agree with Kenn in terms of graphics capability. The graphics on the other systems are much better but that doesn't stop me from playing 'old school' games because I know graphics doesn't ensure you'll have a great game. Graphics can only help enhance immersion into the game but it is gameplay that keeps you going. For example, I played a driving game on the XBOX 360 and I was amazed at the grahical detail the devs put into creating the environment but I got bored with it in 10 minutes as it turned out to be another speed chase driving game. One that has been made before millions of times, starting with Driver and GTA.
I wonder who would be interested in playing a game that first came out on the SNES and didn't change much except for graphics. Sad but true. Now we have so many FPS that all have the same goal - kill as many enemies you can see on the screen and get through the level to reach the next level. It was a fun game at first but now that there are so many on the net and on video games, it sure does get very repetitive and boring. Don't get me wrong, I don't mind FPS but if its a new genre FPS like Metroid Prime or Unreal Tournament or Counter Strike then I'd be happy to play it. But I don't want to play the same old games like Halo and Timesplitters or many of the FPS you see on the Playstation section in video game shops.
I tried Halo and I must say its incredibly difficult to get the hang of using two separate joysticks to move your character on the screen- that was a big turn off factor for trying out many FPS that are out on the market nowdays. The keyboard and mouse is alot more fun for FPS.