Wii's are popular I think as it's more of a "family" console, and the initial purchase price is more appealing. Quite a few of the girls in the office have one. One has kids, the other 2 just like it to muck about on with their partners. Wii sports and they keep going on about how old they are on it.
I have a PSP and PS2 myself. I have GTA3, Vice City, Liberty city stories etc. Great fun. Don't tend to do much of the missions, I quite like the sniper rifle and prefer to go on killing sprees and avoiding the cops myself. Shame GTA4 isn't coming on the PS2, but I'm not going to get a PS3, as although tempting, after a few months I know it'll sit there gathering dust.
Might ask for a Wii for my birthday though. That'll keep me entertained for hours, and I know I can rope the other half into playing that with me. He's never been interested in the PS2, and it's no fun anymore playing on your own.