From a development standpoint, most developers hated the PS2. But when someone looks at the console from a sales standpoint, it was by far the best choice. It could sell games of every genre, and well too.
The reason Metacritic and Gamerankings have become so important to PS360 games is because the systems are expensive, and so are many of the games. Would you want to buy a 60 dollar game that's mediocre? Achievements alleviated this problem somewhat, but only to a small degree.
What you may forget is that the PS2 had a humongous amount of casual gamers, which is why you'll see games like Spongebob selling millions of copies (don't forget about the Rugrats game that broke 3 million copies on the PS1). I don't think we'll be seeing anything like that from the Wii, at least not any time soon.
By the way, the Wii breaks this rule and sells tons of games. If developers feels like costs are really "rising," they can work on the DS or PSP. It's not difficult, and a lot of companies find success on these two platforms (well, the PSP a lot less so).
You should wait until one one of the home consoles this generation has 8 years and the market and a 120 million userbase before completely passing judgment. I'm sure the PS2 will hold the record for most million sellers for a long time, but the Wii and DS have already shown their ability to sell tons of software (and the Xbox 360 to a lesser extent).
