As others have pointed out, the Wii, PS3, and Xbox 360 are "next-gen" gaming consoles and the DS Lite is a portable like the PSP. Due to that, it doesn't really belong in this poll but it would fit perfectly in a PSP/DS Lite poll.
I don't have any of them yet, and might not ever get one. I like the PS3 because you can install another operating system from the menu. Instead of discouraging people from doing this, they make it easier for them. They seem supportive of GNU/Linux and actually sold a Linux kit for the PS2, which is cool although they don't sell it in the USA anymore, which is said to be because of lack of sales.
It's hard for me to know what console is the best until I've actually tried the consoles I have to choose between. I'll probably end up liking the PS3 the most, but I didn't vote for it.
Instead, I voted for the Wii. The Xbox 360 and PS3 aren't bad or anything, but they're the same thing we're used to, just with better graphics. The Wii is the only console that introduces us to something that's unique, and different from what we've had with previous consoles.
There's also a motion sensor in the PS3's controllers, but it seems more like something added on as an extra feature and not something that Sony is completely focused on. The Wii is designed around the single feature, and Nintendo has chosen to make games that are based on that. The PS3 controller is nearly identical to the PS2's, and wouldn't be very good for playing tennis. Pretty graphics seem to be the PS3's main selling point. That's not a bad thing, but I can get pretty graphics on the PC and with the advantage of something more precise than an analog stick: a mouse.
The Wii still gets my vote because it's unique.